循环结构while循环do…while循环for循环package com.fatbread.structure.loopstructure; public class WhileDemo01 { public static void main(String[] args) { //输出1~100 int i 1; while(i100){ i; System.out.println(i); //1~100 } } }package com.fatbread.structure.loopstructure; public class WhileDemo02 { public static void main(String[] args) { //不会停止的循环为死循环 while (true){ //等待客户端连接 //定时检查 //………… } } }package com.fatbread.structure.loopstructure; public class WhileDemo03 { public static void main(String[] args) { //计算123……100 int i 1; int sum 0; while (i100){ sum sumi; i; } System.out.println(sum); //5050 } }package com.fatbread.structure.loopstructure; public class DoWhileDemo01 { public static void main(String[] args) { //计算12………100 int i 1; int sum 0; do { sum sumi; i; }while(i100); //先执行再判断代码至少执行一次 System.out.println(sum); } }package com.fatbread.structure.loopstructure; public class DoWhileDemo02 { public static void main(String[] args) { int i 0; //while和do…while的区别while先判断在执行。dowhile先执行再判断 while (i0){ System.out.println(i); i; } do { System.out.println(i); i; }while (i0); } }package com.fatbread.structure.loopstructure; public class ForDemo01 { public static void main(String[] args) { //while循环 int i 1; //初始化 while(i100) { //判断 System.out.println(i); //循环体 i 2; //迭代 } //for循环 for (int i1 1; i1100; i12){ //初始化判断迭代 System.out.println(i1); //循环体 } //快捷键100.for for (int a 0; a 100; a) { System.out.println(a); /* 先执行初始化。可以声明一种类型也可以初始化一个或多个循环的控制变量可以为空 然后检测布尔表达式的值true则运行false则退出循环 开始执行循环体后面的语句 执行一次循环后返回迭代 迭代后的变量再检测布尔值 */ for ( ; ; ){ } //表示死循环 } } }package com.fatbread.structure.loopstructure; public class ForDemo02 { public static void main(String[] args) { //计算1~100之间奇数和偶数的和 int sum1 0; for (int i 0; i100; i2){ sum1 isum1; } System.out.println(sum1); int sum2 0; for (int a 1; a100; a2){ sum2 sum2a; } System.out.println(sum2); System.out.println(); int oddsum 0; int evensum 0; for (int i1 0; i1 100; i1) { if (i1%20){ evensumi1; }else{ oddsumi1; } } System.out.println(奇数的和为oddsum); System.out.println(偶数的和为evensum); System.out.println(); //用while和for循环输出1~1000之间能被5整除的数并每行输出三个 for (int b 0; b 1000; b) { if (b%50){ System.out.print(b\t); if (b%150){ System.out.println(\n); } } } //println:输出完会换行 //print:输出完不会换行 System.out.println(); int c 0; while(c1000){ c; if (c%50){ System.out.print(c\t); if (c%150){ System.out.print(\n); } } } System.out.println(); } }package com.fatbread.structure.loopstructure; public class ForDemo03 { public static void main(String[] args) { //九九乘法表 for (int a1 1; a110; a1){ for (int d1 0; a1d110; d1){ System.out.print(a1*(a1d1)a1*(a1d1)\t); } System.out.print(\n); } for (int a2 1; a2 10; a2){ for (int d2 1; d2a2; d2){ System.out.print(d2 *a2 d2 *a2\t); } System.out.print(\n); } /* 1.先打印出1*n的第一列 2.再把固定的1用一个循环包起来把1变成1~9的变量 3.去掉重复项 4.修改样式 */ } }package com.fatbread.structure.loopstructure; public class ForDemo04 { public static void main(String[] args) { int[] numbers {10,20,30,40}; //定义了一个数组 //遍历数组的元素 for (int x:numbers){ System.out.println(x); } for (int i 0; i 4; i) { //打印数组中第0到第3位数字 System.out.println(numbers[i]); } } }