for,while,do-while,死循环,嵌套循环,跳转关键字,随机数

 1.for循环

public class ForDemo1 {public static void main(String[] args) {for (int i = 0; i < 5; i++) {System.out.println("HelloWorld");}System.out.println("--------------------------------------------");for (int i = 1; i <=10 ; i++) {System.out.println("HelloWorld1");}System.out.println("--------------------------------------------");for (int i = 1; i <=10 ; i+=2) {System.out.println("HelloWorld2");}}
}

public class ForDemo2 {public static void main(String[] args) {// 目标：打印输出1-100的数据，求1-100的和for (int i = 1; i < 101; i++) {System.out.println(i);}int sum = 0;System.out.println("---------------------------------------");for (int i = 1; i <= 100 ; i++) {sum += i;}System.out.println(sum);System.out.println("----------------------------------------");/*** 计算1-100之间的奇数和*/int sum1 = 0;for (int i = 0; i < 100; i++) {if (i % 2 == 1){sum1 += i;}}System.out.println(sum1);}
}

 2.while循环

// while循环
public class WhileDemo3 {public static void main(String[] args) {int i = 0;while (i < 5){System.out.println("HelloWorld");i++;}}
}

 3.do-while循环

public class DoWhileDemo5 {public static void main(String[] args) {int i = 0;do {System.out.println("HelloWorld");}while (i < 0);// while循环中的变量可以在while外部使用System.out.println(i);// 而for中定义的变量只能在for循环中使用，不能在外部使用for (int j = 0;j < 4;j++){System.out.println(j);}// System.out.println(j);  报错}
}

 4.死循环

public class EndLessLoopDemo6 {public static void main(String[] args) {// 死循环的三种写法/*for (; ;) {System.out.println("HelloWorld");}*//*  while (true){System.out.println("HelloWorld1");}*//*      do {System.out.println("HelloWorld");}while (true);*/}
}

5.嵌套循环 

public class LoopNestedDemo7 {public static void main(String[] args) {for (int i = 0; i < 3; i++) {for (int j = 0; j < 5; j++) {System.out.println("抽死你");}System.out.println("----------------------------------");}for (int i = 0; i < 3; i++) {for (int j = 0; j < 4; j++) {System.out.print("*");}System.out.println();   // 换行}}
}

6.跳转关键字 

public class BreakAndContinueDemo8 {public static void main(String[] args) {// 目标：掌握break和continue的执行// 1.break:跳出并结束当前所在循环for (int i = 1; i <= 5; i++) {System.out.println("。。。");if (i == 3) {break;}}for (int i = 0; i < 5; i++) {System.out.println("。。。");if (i == 2) {break;}}for (int i = 0; i < 5; i++) {if (i == 3) {break;}System.out.println("。。。");}// 2.continue:提出本次循环，执行下一次循环// 第一天干活，第二天干活，第三天休息，第四天干活for (int i = 1; i <= 4; i++) {if (i == 3){System.out.println("第"+i+"天休息");continue;}else {System.out.println("第"+i+"天干活");}}}
}