吃不饱的刘某人
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- Who say what
- 算术运算符的使用
- 位运算符的使用
- 关系运算符的使用
- 逻辑运算符的使用
- 数据类型转换
- 全局变量和局部变量
- 比较两个数的大小
- 给成绩评定等级
- 计算数学分段函数
- 使用switch给成绩评定等级
- 10的阶乘
- 求和1+1/2-1/3+......+1/100
- 求和1！+2！+3！+4！+5！
- 用do-while计算10！
- 求50~100之间所有素数的程序，目的是演示一下break语句的使用
- 使用continue语句，计算10以内的奇数的和
- 计算四位数，前两位一样，后两位一样
- 判断一个正整数是否是素数，若是计算其阶乘
- 创建对象与field的访问
- 简单数据类型作参数,计算立方体体积
- 圆形类CCircle，计算圆的面积
- 对象类型作参数
- 参数的单向值传递
- 共有成员(method)的建立
- 私有成员无法从类外部来访问的范例
- 构造方法的定义与使用
- static定义静态变量
- 通过类名访问类方法
- 建立获取对象名字的成员方法getName和获取对象性别的成员方法getSex，以及输出对象的全部成员方法studPrint
- 从一组号码1，2，3……high中，抽出一组幸运号码，将幸运号码作为方法的返回值返回
- 求一维数组的最大值和最小值
- 二维数组的赋值与输出
- 求二维数组的最大值
- 三维数组
- 子类可以继承父类的所有非私有数据成员
- 子类中的同名属性对父类同名属性的隐藏
- 子类同名方法对父类同名方法的覆盖
- 子类对父类方法的继承
- super的使用
- 方法的重载
- 构造方法的继承
- 构造方法的重载
- 抽象类的实例
- 用抽象类类型的变量来建立对象
- 利用父类的变量数组来访问子类里的内容
- 接口的实现范例
- 实现两个以上的接口
- 接口的扩展
- 在构造函数里建立内部类的对象
- final修饰数据成员
- final修饰的最终方法
- System的范例：请输入一个字符
- object类的范例
- 数学类
- 字符串类
- 判断大小写
- Calendar类的应用范例
- Random类的范例。随机产生1~6之间的随机整数，统计各数出现的概率
- 一个简单的框架窗口
- 通过继承JFrame类实现的窗口（疑惑？）
- 向框架窗口中添加按钮组件
- BorderLayout的布局的应用
- GridLayout布局的应用
- 向FlowLayout布局的容器中添加多个大小不同的组件
- 通过容器的嵌套实现较复杂的布局
- text（you click the button ok）
Who say what
class WhoSayWhat { public static void main(String args[ ]) { if(args.length < 2) { System.out.println("请向应用程序传递两个参数"); System.exit(0); } String s1 = args[0]; String s2 = args[1]; System.out.println(s1 + " Say：" + s2); }}
算术运算符的使用
public class ArithOp { public static void main(String[ ] args) { int a = 7 + 2;int b = a*2; int c = b / 9; int d = - a; int e = d % 2; double f = 17.5 / 4; int i = 2; int j = i ++; int k = ++ i; System.out.println("a=" + a); System.out.println("b=" + b); System.out.println("c=" + c); System.out.println("d=" + d); System.out.println("e=" + e); System.out.println("f=" + f); System.out.println("i=" + i); System.out.println("j=" + j); System.out.println("k=" + k);}}
位运算符的使用
public class BitOp { public static void main(String[ ] args) { int a = 9; int b = 15; int c = 8; int d,e,f,g,h; d = a & b; e = a | b; f = a ^ b; g = a << 2; h = c >> 1; System.out.println("d=" + d); System.out.println("e=" + e); System.out.println("f=" + f); System.out.println("g=" + g); System.out.println("h=" + h);}}
关系运算符的使用
public class RelationOp { public static void main(String[ ] args) {int a = 9; int b = 6;int c = 6; boolean d = a > b; boolean e = a < b; boolean f = b == c; boolean g = b != c; boolean h = b >= c; boolean i = b <= c; boolean j = a == b; System.out.println("d=" + d);System.out.println("e=" + e);System.out.println("f=" + f);System.out.println("g=" + g);System.out.println("h=" + h);System.out.println("i=" + i);System.out.println("j=" + j); }}
逻辑运算符的使用
public class LogicOp { public static void main(String[ ] args) { int a = 9; int b = 6; int c = 6; boolean d,e,f,g; d = ! (a > b); e = (a > b) && (a > c); f = (b == c) || (a < b); g = (b == c) && (a < b); System.out.println("d=" + d); System.out.println("e=" + e); System.out.println("f=" + f); System.out.println("g=" + g); }}
数据类型转换
public class TypeConversion { public static void main(String[ ] args) { char a = 1; byte b = 2; short c = 3;int d = 4; byte e; e = (byte)(a + b + c + d); short f; f = (short)(a + b + c + d); int g; g = a + b + c + d; float h; h = a + b + c + d; double i; i = a + b + c + d; System.out.println("e = " + e); System.out.println("f = " + f); System.out.println("g = " + g); System.out.println("h = " + h); System.out.println("i = " + i);}}
全局变量和局部变量
public class SetVariable{static double pi = 3.141592654；static short s1; static int i1; static long l1; static char ch1; static float f1; static double d1; static boolean b1; public static void main(String args[]) {short s2 = 35;int i2 = -32;long l2 = 34555L;char ch2 = 'A';float f2 = 897.89F;double d2 = 34.345;boolean b2 = false;System.out.println("数学常量pi = " + pi); System.out.println("局部变量");System.out.println("短整型变量s2 = " + s2);System.out.println("整型变量i2 = " + i2);System.out.println("长整型变量l2 = " + l2);System.out.println("字符变量ch2 = " + ch2);System.out.println("浮点数类型f2 = " + f2);System.out.println("双精度型变量d2 = " + d2);System.out.println("布尔型变量b2 = " + b2); change();System.out.println("全局变量");System.out.println("短整型变量s1 = " + s1);System.out.println("整型变量i1 = " + i1);System.out.println("长整型变量l1 = " + l1);System.out.println("字符变量ch1 = " + ch1);System.out.println("浮点数类型f1 = " + f1);System.out.println("双精度型变量d1 = " + d1);System.out.println("布尔型变量b1 = " + b1);} public static void change() {s1 = 125;i1 = 88;l1 = 987654321L;ch1 = 'B';f1 = 3.2590F;d1 = -1.04E-5;b1 = true; }}
比较两个数的大小
public class Ifdemo1 { public static void main(String[ ] args) { int i1 = 8, i2 = 5; if(i1 >= i2) System.out.println(i1 + ">=" + i2);else System.out.println(i1 + "<" + i2); }}
给成绩评定等级
public class IfDemo2 {public static void main(String[ ] args) {int testscore = 78; char grade;if (testscore >= 90) grade = 'A';else if (testscore >= 80)grade = 'B';else if (testscore >= 70) grade = 'C';else if (testscore >= 60) grade = 'D';else grade = 'E';System.out.println("Grade = " + grade); }}
计算数学分段函数
public class Ifdemo3 { public static void main(String[ ] args) { int x = 4; float y; if(x <= 0) y = x + 8; else if(x <= 6) y = 3 * x-21; else y = 8 * x * x - 9; System.out. println("y = " + y); }}
使用switch给成绩评定等级
public class SwitchDemo { public static void main(String[ ] args) { int testscore = 78; char grade; switch(testscore / 10) { case 10: case 9: grade = ' A'; break; case 7: grade = 'C'; break; case 6: grade = 'D'; break; default: grade = 'E'; } System.out.println("Grade = " + grade);}}
10的阶乘
public class ForOp1 {public static void main(String[ ] args){long result = 1;for(int i = 10; i > 0; i--) result *= i ;System.out.println("10!=" + result);}}
求和1+1/2-1/3+…+1/100
public class ch2 {public static void main(String[ ] args) {int m = 1; double s = 0; for(int i = 1;i <= 100;i ++) { s = s + m * 1.0 / i; m = - m; } System.out.println("s =" + s);}}
求和1！+2！+3！+4！+5！
public class ch3n {public static void main(String[ ] args) { int i,t,s=0; for(i = 1,t = 1;i <= 5;i ++) { t = t *i;s + = t; } System.out.println(" s = " + s);}}
用do-while计算10！
public class DoWhileDemo {public static void main(String[ ] args){int n = 10;long result = 1;do result * = n--;while(n >= 1);System.out.println("10!=" + result);}}
public class WhileDemo {public static void main(String[ ] args){int n = 10;long result = 1;while(n >= 1) result * = n--;System.out.println("10! = " + result);}}
求50~100之间所有素数的程序，目的是演示一下break语句的使用
public class Prime50_100Exam{ public static void main(String[] args) {int n,m,i; for( n=50; n<100; n++){for( i=2; i<=n/2; i++){if(n%i==0) break; } if(i>n/2) { System.out.print(n+" "); } } }}
使用continue语句，计算10以内的奇数的和
public class ContinueOp{public static void main(String[ ] args){int s = 0;for(int i = 1;i <=10;i ++) {if (i % 2 == 0) continue; s += i ; }System.out.println("s = " + s);}}
计算四位数，前两位一样，后两位一样
public class first {public static void main(String[] args) {int a,i,x,y,z,t; for( i=32; i<100; i++){ a=i*i; x=a/1000; y=a/100%10; z=a/10%10; t=a%10; if(x==y&&z==t) { System.out.print(i+"的平方是"+a); } } }}
判断一个正整数是否是素数，若是计算其阶乘
public class Math_mothodExam{public static boolean prime(int n){ for(int i=2; i<n/2; i++){ if(n%i==0) return false; }return true; } public static int factorial(int n){ if(n<=1) return 1;int m=1;for(int i=1; i<=n; i++) m*=i;return m;} public static void main(String args[]){ int n=13;System.out.println(n+"是素数吗？"+prime(n));if(prime(n)) System.out.println(n+"!="+factorial(n));} }
创建对象与field的访问
class CRectangle{ int width; int height; }public class app7_1{public static void main(String args[]){CRectangle rect1;rect1=new CRectangle(); rect1.width=10; rect1.height=5; System.out.println("width="+rect1.width); System.out.println("height="+rect1.height); }}
简单数据类型作参数,计算立方体体积
class cube{double width;double height;double depth;double volume() { return width * height * depth; } void setParam(double x,double y,double z) {width = x; height = y;depth = z; } } public class Usecube {public static void main(String args[ ]) {double v;cube mycube = new cube(); mycube.setParam(4,6,8); v = mycube.volume(); System.out.println("mycube.volume = " + v); } }
圆形类CCircle，计算圆的面积
class CCircle { double pi; double radius; double getRadius(){ return radius; } void setCircle(double r, double p){ pi=p; radius=r; }}public class Ccircle_main{ public static void main(String args[]) { CCircle cir1=new CCircle(); cir1.setCircle(2.0,3.1416); System.out.println("radius="+cir1.getRadius()); }}
对象类型作参数
class Point {int x,y;}class Carry{ void fun(Point p) { p.x += p.y; p.y *= 5; }}public class UsePoint {public static void main(String args[ ]){carry s = new carry();point p = new Point();p.x = 3;p.y = 5;s.fun(p);System.out.println("p.x = " + p.x + ", p.y = " + p.y); }}
参数的单向值传递
public class Carry { static void fun(int x,int y) {x = x + y;y = 5 * y; System.out.println("x = " + x + ", y = " + y);} public static void main(String args[ ]) {int a = 3;int b = 5;fun(a,b);System.out.println("a = "+a+", b = " + b); }}
共有成员(method)的建立
class CCircle { private double pi=3.14; private double radius; public void show_area(){ System.out.println("area="+pi*radius*radius); } public void setRadius(double r){ if(r>0){ radius=r; System.out.println("radius="+radius); } else System.out.println("input error"); } }public class Gongyou{ public static void main(String args[]) { CCircle cir1=new CCircle(); cir1.setRadius(-2.0); cir1.show_area(); }}
私有成员无法从类外部来访问的范例
class CCircle { private double pi=3.14; private double radius; void show_area(){ System.out.println("area="+pi*radius*radius); }}public class Siyou{ public static void main(String args[]) { CCircle cir1=new CCircle(); cir1.radius=-2.0; cir1.show_area(); }}
构造方法的定义与使用
class Dog {private int weight; public Dog() { weight = 42; }public int getWeight() {return weight;} }public class UseDog {public static void main(String args[ ]) {Dog d = new Dog();System.out.println("The dog’s weight is " + d.getWeight());} }
static定义静态变量
class SDemo {int x; static int y;}public class StaticDemo {public static void main(String arg[ ]) {SDemo ob1 = new SDemo();SDemo ob2 = new SDemo();ob1.x = 10; ob2.x = 20; System.out.println("Of course ,ob1.x and ob2.x "+ob1.x+ob2.x); System.out.println("The static var is shared"); ob1.y = 19; System.out.println("ob1.y=" + ob1.y); System.out.println("ob2.y=" + ob2.y); SDemo.y = 11; System.out.println("SDemo.y = " + SDemo.y); System.out.println("ob1.y = " + ob1.y); System.out.println("ob2.y = " + ob2.y);}}
通过类名访问类方法
class SMeth{static int val=1024;static int valDiv2(){return val / 2; } }public class Staicmeth {public static void main(String args[ ]) {System.out.println("Val is" + SMeth.val);System.out.println("StaticMeth.valDiv2():" + SMeth.valDiv2());}}
建立获取对象名字的成员方法getName和获取对象性别的成员方法getSex，以及输出对象的全部成员方法studPrint
class Student {private String name; private char sex; private double score; Student (String cname,char csex,double cscore) {name = cname; sex = csex; score = cscore; }String getName() {return name;} char getSex() { return sex; }void studPrint() {System.out.println("Name:" + name + "\tSex:" + sex + "\tScore:" + score); }}public class rrOb {public static void main(String args[ ]) { String mname; char msex; int len; Student[ ] st1 = new Student[3];st1[0] = new Student("Li", 'F',89);st1[1] = new Student("Zhang", 'M',90);st1[2] = new Student("Zhou", 'F',98);for(int i = 0; i < st1.length; i ++) st1[i].studPrint();mname = st1[1].getName();msex = st1[1].getSex();System.out.println("Name 1:" + mname + "\t" + msex);}}
从一组号码1，2，3……high中，抽出一组幸运号码，将幸运号码作为方法的返回值返回
import java.util.Arrays;public class RandomA { public static int [ ] drawing(int high,int number) {int I; int numbers[ ] = new int [high]; int result[ ] = new int [number]; for(i = 0;i < high;i ++) numbers[I] = i +1;for(i = 0;i < number;i ++) { int j = (int)(Math.random()*(high-i)); result[i] = numbers[j]; numbers[j] = numbers[high-1-i]; }return result; }public static void main(String args[ ]) { int numbers = 7; int topNumber = 36; int a[ ] = drawing(topNumber,numbers);Arrays.sort(a); System.out.print("Lucky numbers are: ");for(int i = 0;i < a.length; i ++) System.out.print(" " + a[i]);System.out.println();}}
求一维数组的最大值和最小值
public class Arraymax { public static void main(String args[ ]) {int table[ ] = {21,34,65,38,24,46,29,64,75,92};int i,max,min;System.out.print("Table: ");for(i = 0;i < table.length;i ++)System.out.print(" " + table[i]);System.out.println();max =min = table[0];for(i = 1; i < table.length; i ++){ if(table[i] > max) max = table[i];else if(table[i] < min) min = table[i]; }System.out.println("Max=" + max);System.out.println("Min=" + min);}}
二维数组的赋值与输出
public class ArrIO { public static void main(String args[ ]) { int a[ ][ ] = new int[4][ ]; for(int I = 0;I < a.length;I ++) {a[I] = new int[5]; for(int j = 0;j < a[I].length;j ++) a[I][j] = I+j; } for(int k = 0;k < a.length;k ++) {for(int n = 0;n< a[k].length;n ++) System.out.print("a["+k+"]["+n+"]=" + a[k][n] + " "); System.out.println(); }} }
求二维数组的最大值
class Maxvalue {int maxv(int arr1[ ][ ]) {int i,j,max;max = arr1[0][0];for(i = 0; i < arr1.length; i ++) for( j = 0;j < arr1[i].length; j ++) if(arr1[i][j] > max) max = arr1[i][j];return max; }}public class ArrMax {public static void main(String args[ ]) {int a[ ][ ] ={{1,3,5},{2,5,7,8},{8,3,4,6,9}};int max;Maxvalue p = new Maxvalue();max = p.maxv(a);System.out.println("max=" + max);}}
三维数组
public class Sanwei{ public static void main(String args[]){ int i,j,k,sum=0; int A[][][]={{{5,1},{6,7}},{{9,4},{8,3}}}; for(i=0;i<A.length;i++)for(j=0;j<A[i].length;j++)for(k=0;k<A[j].length;k++){ System.out.print("A["+i+"]["+j+"]["+k+"]="); System.out.println(A[i][j][k]); sum+=A[i][j][k]; }System.out.println("sum="+sum); }}
子类可以继承父类的所有非私有数据成员
class A1{int x = 25;private int z; }public class SubDemo1 extends A1{public static void main(String args[ ]) {subDemo1 p = new subDemo1();System.out.println("p.x = " + p.x); System.out.println(“p.z = ” + p.z); }}
子类中的同名属性对父类同名属性的隐藏
class A {int x1 = 10;float x2 = 2.0f;}class B extends A {int x1 = 15;int x2 = 25;String x3 = "hello";}public class C {public static void main(String args[ ]) {A p1 = new A();B p2 = new B();System.out.println("A:" + p1.x1 + p1.x2);System.out.println("B:" + p2.x1 + p2.x2 + p2.x3);}}
子类同名方法对父类同名方法的覆盖
class A {int fun(int a,int b) {return a * b;}}class B extends A {int fun(int c,int d) { return c + d;}}public class C2 {public static void main(String args[ ]) {B s = new B();System.out.println("s = " + s.fun(10,20));}}
子类对父类方法的继承
class A2 {int x = 0,y = 1;void print1() {System.out.println("x = " + x + "y = " + y); }private void print2() {System.out.println("x = " + x + "y = " + y); } }public class SubDemo2 extends A2 {public static void main(String args[ ]) { int z = 3; SubDemo2 p = new SubDemo2(); p.print1(); p.print2(); } }
super的使用
class A {int x1 = 10;float x2 = 2.0f;void show(){ System.out.println("1 A:" + "x1 = " + x1 + "x2 = " + x2);}}class B extends A {int x1 = 15;int x2 = 25;void show() {System.out.println("2 A:" + "x1 = " + super.x1 + "x2 = " + super.x2);super.show(); System.out.println("3 B:" + "x1 = "+ x1 + "x2 = " + x2);}}public class SuperDemo {public static void main(String args[ ]) {A p = new A();B q = new B();p.show();q.show();}}
方法的重载
class A {int add(int a,int b) {return a + b; }double add(double a,double b) { return a + b; }double add(double a,double b,double c) { return a + b + c;}}public class OverloadDemo {public static void main(String args[ ]) {A p = new A();System.out.println("Sum is " + p.add(3.8,5.3));System.out.println("Sum is " + p.add(3,5));System.out.println("Sum is " + p.add(3.8,5.3,7.2));}}
构造方法的继承
class AddClass {public int x = 0,y = 0,z = 0;AddClass (int x) { this.x = x;} AddClass (int x,int y){ this.x = x; this.y = y; }AddClass (int x,int y,int z){ this.x = x; this.y = y; this.z = z; }public int add() { return x + y + z; }}public class Subconstruct extends AddClass {int a = 0,b = 0,c = 0;Subconstruct(int x) { super(x); a = x + 7;}Subconstruct(int x,int y) { super(x,y); a = x + 5; b = y + 5; } Subconstruct(int x,int y,int z) { super(x,y,z); a = x + 4; b = y +4; c = z + 4; } public int add() { System.out.println("super: x + y + z = " + super.add());return a + b + c; } public static void main(String args[ ]) { Subconstruct p1 = new Subconstruct (2,3,5); Subconstruct p2 = new Subconstruct (10,20); Subconstruct p3 = new Subconstruct (1); System.out.println("a + b + c = " + p1.add()); System.out.println("a + b= " + p2.add());System.out.println("a = " + p3.add());}}
构造方法的重载
class AddClass {public int x = 0,y = 0,z = 0;AddClass (int x) { this.x = x; }AddClass (int x,int y) { this(x); this.y = y; }AddClass (int x,int y,int z){ this(x,y); this.z = z; } public int add() { return x+y+z;}}public class ConstructOver {public static void main(String args[ ]) {AddClass p1 = new AddClass (2,3,5); AddClass p2 = new AddClass (10,20); AddClass p3 = new AddClass (1); System.out.println(" x + y + z = " + p1.add()); System.out.println(" x + y = " + p2.add()); System.out.println(" x = " + p3.add());}}
抽象类的实例
abstract class CShape { protected String color; public void setColor(String str){ color=str; } abstract void show(); }class CRectangle extends CShape { int width,height; public CRectangle(int w,int h){ width=w; height=h; } public void show(){ System.out.print("color="+color+", "); System.out.println("area="+width*height); }}class CCircle extends CShape { double radius; public CCircle(double r){ radius=r; } public void show(){ System.out.print("color="+color+", "); System.out.println("area="+3.14*radius*radius); }}public class app1{ public static void main(String args[]) { CRectangle rect=new CRectangle(5,10); rect.setColor("Yellow"); rect.show(); CCircle cir=new CCircle(2.0); cir.setColor("Green"); cir.show(); }}
用抽象类类型的变量来建立对象
public class app2{ public static void main(String args[]){ CShape shape1=new CRectangle(5,10);shape1.setColor("Yellow"); shape1.show(); CShape shape2=new CCircle(2.0);shape2.setColor("Green");shape2.show(); }}
利用父类的变量数组来访问子类里的内容
public class app3{ public static void main(String args[]) { CShape shape[]; shape=new CShape[2]; shape[0]=new CRectangle(5,10);shape[0].setColor("Yellow"); shape[0].show(); shape[1]=new CCircle(2.0);shape[1].setColor("Green");shape[1].show(); }}
接口的实现范例
interface iShape2D{ final double pi=3.14; abstract void area();}class CRectangle implements iShape2D{ int width,height; public CRectangle(int w,int h){ width=w; height=h; } public void area(){ System.out.println("area="+width*height); }}class CCircle implements iShape2D{ double radius; public CCircle(double r){ radius=r; } public void area(){ System.out.println("area="+pi*radius*radius); }}public class app4{ public static void main(String args[]){ CRectangle rect=new CRectangle(5,10); rect.area(); CCircle cir=new CCircle(2.0); cir.area(); }}
实现两个以上的接口
interface iShape2D { final double pi=3.14; abstract void area();}interface iColor { abstract void setColor(String str);}class CCircle implements iShape2D,iColor { double radius; String color; public CCircle(double r){ radius=r; } public void setColor(String str){ color=str; System.out.println("color="+color); } public void area(){ System.out.println("area="+pi*radius*radius); }}public class app5{ public static void main(String args[]) { CCircle cir; cir=new CCircle(2.0);cir.setColor("Blue"); cir.area(); }}
接口的扩展
interface iShape { final double pi=3.14; abstract void setColor(String str);}interface iShape2D extends iShape { abstract void area();}class CCircle implements iShape2D { double radius; String color; public CCircle(double r){ radius=r; } public void setColor(String str){ color=str; System.out.println("color="+color); } public void area(){ System.out.println("area="+pi*radius*radius); }}public class app6{ public static void main(String args[]) { CCircle cir; cir=new CCircle(2.0);cir.setColor("Blue");cir.area(); }}
在构造函数里建立内部类的对象
public class inner{ public inner(){ Caaa aa= new Caaa(); aa.set_num(5); } public static void main(String args[]){ inner obj=new inner(); } class Caaa{ int num; void set_num(int n){ num=n; System.out.println("num= "+ num);} } }
final修饰数据成员
class ca {static int n = 20;final int nn; final int k = 40; ca() { nn = + + n; }}public class finalDemo1 {public static void main(String args[ ]) { ca m1 = new ca(); ca m2 = new ca(); m1.nn = 90; System.out.println("m2.nn = " + m2.nn); System.out.println("m2.k = " + m2.k); System.out.println("m1.nn = " + m1.nn); System.out.println("m1.k = " + m1.k);}}
final修饰的最终方法
class a1 {final int add(int x,int y) {return x + y;}int mul (int a,int b) {int z = 0; z = add(1,7) + a * b; return z;}}public class finalDemo2 extends a1 {int add(int x,int y) { return x + y + 2;} public static void main(String args[ ]) {int a = 2,b = 3,z1,z2;finalDemo2 p1 = new finalDemo2();z1 = p1.add(a,b);z2 = p1.mul(a,b); System.out.println("z1 = " + z1);System.out.println("z2 = " + z2);}}
System的范例：请输入一个字符
public class SystemD {public static void main(String args[ ]) throws Exception {char c;System.out.println("请输入一个字符:");c = (char)System.in.read();System.out.println("你输入字符:" + c);}}
object类的范例
public class ObjectD {public static void main(String[ ] args) {Integer a = new Integer(1); Integer b = new Integer(1); System.out.println(a.equals(b)); System.out.println("The Object’s class is: " + a.getClass());} }
数学类
class MathD {public static void main(String args[ ]) {System.out.println("Math.E=" + Math.E);System.out.println("Math.PI=" + Math.PI);System.out.println("sin(pi/2) =" + Math.sin(Math.PI/2));System.out.println("ceil(E)=" + Math.ceil(Math.E)); System.out.println("rint(PI)=" + Math.rint(Math.PI)); System.out.println("round(PI)=" + Math.round(Math.PI)); int I = (int)(Math.random()*10) + 1;System.out.println("i =" + i );System.out.println("exp(1)=" + Math.exp(1));System.out.println("lnE=" + Math.log(Math.E));System.out.println("sqrt(" + 25 + ")=" + Math.sqrt(25));System.out.println("power(" + 2 + "," + 8 + ")=" + Math.pow(2,8));System.out.println("abs(-8.2)=" + Math.abs(-8.2));System.out.println("max("+2+"."+"8)=" + Math.max(2,8));System.out.println("min("+2+"."+"8)=" + Math.min(2,8));}}
字符串类
public class StringD {public static void main(String args[ ]) {String s1 = "Java "; String s2 = "java"; String s3 = "Welcome"; String s4 = "Welcome"; String s5 = "Welcoge"; String sc1 = s3.concat(s1);String sc2 = s1.concat("abx"); String str1 = s3.replace('e', 'r'); String w1 = s5.toLowerCase() ;String u2 = s2.toUpperCase();System.out.println("s1=" + s1 + "\t s2=" + s2);System.out.println("s3=" + s3+"\t s4=" + s4);System.out.println("s5=" + s5);System.out.println("s3+s1=" + sc1);System.out.println("s1+abx=" + sc2);System.out.println("s3.replace('e', 'r')= " + str1);System.out.println("s5.toLower=" + w1);System.out.println("s2.toUpper=" + u2);}}
判断大小写
public class CharacterD {public static void main(String args[ ]) {Character ch = new Character('a'); char c = ch.charValue();if(Character.isUpperCase(c))System.out.println("The character " + c + " is upper case.");else System.out.println("The character" + c + "is lower case.");boolean b = Character.isDigit(c);int x = Character.digit('c',16);System.out.println("b=" + b);System.out.println("x=" + x);}}
Calendar类的应用范例
import java.util.*;class CalendarD {public static void main(String args[ ]) {Calendar now = Calendar.getInstance();int ampm = now.get(Calendar.AM_PM);int hour = now.get (Calendar.HOUR_OF_DAY);int day = now.get (Calendar.DAY_OF_MONTH);System.out.println(ampm);System.out.println(hour);System.out.println(day);}}
Random类的范例。随机产生1~6之间的随机整数，统计各数出现的概率
import java.util.*;class RandomDemo {public static void main(String args[ ]) {Random rd = new Random();int[ ] fre = new int[6];int rdGet;for(int i = 0; i <= 100; i ++) {rdGet = Math.abs(rd.nextInt()) % 6 + 1;switch(rdGet) {case 1:fre[0] ++;break;case 2:fre[1] ++;break;case 3:fre[2 ]++;break;case 4:fre[3] ++;break;case 5:fre[4] ++;break;case 6:fre[5] ++;break;}}for(int j = 0; j < fre.length; j ++){ System.out.println((j+1) + "出现的次数" + fre[j] + "出现的比率：" + fre[j] / 10.0 + "% ");}}
一个简单的框架窗口
import javax.swing.*;public class SimpleFrame{public static void main(String args[]){JFrame frame=new JFrame("Simple Frame "); frame.setSize(350,240); frame.setVisible(true);} }
通过继承JFrame类实现的窗口（疑惑？）
import javax.swing.*;public class SimpleFrame extends JFrame{ public SimpleFrame(){ this("No Title"); } public SimpleFrame(String title){ super(title); setSize(350,240); setLocation(350,250); setVisible(true); setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); } }public class SimpleFrameTest{ public static void main(String args[]){ SimpleFrame frame=new SimpleFrame("Simple Frame"); }}
向框架窗口中添加按钮组件
import java.awt.Container;import javax.swing.*;public class FrameWithButton extends JFrame{ JButton jButton1,jButton2; Container cp=null;public FrameWithButton(){ this(“No Title”); } public FrameWithButton(String title){ super(title); jButton1 = new JButton(“OK”); jButton2 = new JButton(“Cancel”); cp = getContentPane(); cp.add(jButton1); cp.add(jButton2); setSize(400,300); setVisible(true); setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);} public static void main(String[] args){ JFrame frame = new FrameWithButton("Frame With Button");} }
BorderLayout的布局的应用
import java.awt.*;import javax.swing.*;public class BorderDemo extends JFrame { JButton jButton1,jButton2, jButton3,jButton4,jButton5; public BorderDemo() { Container cp = getContentPane(); jButton1 = new JButton("North"); jButton2 = new JButton("South"); jButton3 = new JButton("West"); jButton4 = new JButton("East"); jButton5 = new JButton("Center"); cp.add(jButton1, BorderLayout.NORTH); cp.add(jButton2, BorderLayout.SOUTH); cp.add(jButton3, BorderLayout.WEST); cp.add(jButton4, BorderLayout.EAST); cp.add(jButton5, BorderLayout.CENTER); setSize(400,300); setTitle("BorderLayout Demo"); setVisible(true);setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); } public static void main(String args[]) { BorderDemo window = new BorderDemo();}}
GridLayout布局的应用
import java.awt.*;import javax.swing.*;public class GridWindow extends JFrame { public GridWindow() { Container cp = getContentPane(); cp.setLayout(new GridLayout(0,2)); cp.add(new JButton("Button 1")); cp.add(new JButton("2")); cp.add(new JButton("Button 3")); cp.add(new JButton("Long-Named Button 4")); cp.add(new JButton("Button 5")); } public static void main(String args[]) { GridWindow window = new GridWindow(); window.setTitle("GridLayout"); window.pack(); window.setVisible(true); }}
向FlowLayout布局的容器中添加多个大小不同的组件
import java.awt.*;import javax.swing.*;public class FlowWindow extends JFrame { public FlowWindow() { Container cp = getContentPane(); FlowLayout layout = new FlowLayout(FlowLayout.CENTER,10,20);cp.setLayout(layout); cp.add(new JButton("Button 1")); cp.add(new JButton("2")); cp.add(new JButton("Button 3")); cp.add(new JButton("Long-Named Button 4")); cp.add(new JButton("Button 5")); setSize(400,300); setVisible(true); setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); } public static void main(String args[]) { FlowWindow window = new FlowWindow(); }}
通过容器的嵌套实现较复杂的布局
import java.awt.*;import javax.swing.*;public class FrameWithPanel extends JFrame{JButton btn1,btn2,btn3;Container cp = null;JPanel panel_1,panel_2;public FrameWithPanel(){ super("Frame With Panel");btn1 = new JButton("Red");btn2 = new JButton("Green");btn3 = new JButton("Blue");panel_1 = new JPanel();panel_1.setBackground(Color.CYAN);panel_2 = new JPanel();panel_2.setLayout(new FlowLayout(FlowLayout.CENTER,20,10));cp=getContentPane();panel_2.add(btn1);panel_2.add(btn2);panel_2.add(btn3);cp.add(panel_1,BorderLayout.CENTER);cp.add(panel_2,BorderLayout.SOUTH);setSize(300,200);}public static void main(String args[]){FrameWithPanel frame = new FrameWithPanel ();frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);frame.setVisible(true);}}
text（you click the button ok）
import java.awt.*;import java.awt.event.*;import javax.swing.*;public class EventDemo extends JFrame implements ActionListener{JTextField tf ;JButton btn1,btn2; public EventDemo(){ super("Event Demo");tf = new JTextField(20); btn1 = new JButton("OK"); btn2 = new JButton("Cancel"); container cp = getContentPane(); cp.setLayout(new FlowLayout()); cp.add(tf); cp.add(btn1); cp.add(btn2); btn1.addActionListener(this); btn2.addActionListener(this); } public void actionPerformed(ActionEvent e){ if((JButton)e.getSource()==btn1) tf.setText("you clicked button OK");else if((JButton)e.getSource()==btn2) tf.setText("you clicked button Cancel"); } public static void main(String[]args){EventDemo frame = new EventDemo(); frame.setSize(400,100); frame.setLocation(200,200); frame.setVisible(true); frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); }}
