【Java基础】流程控制语句

怼烎@ 2024-03-26 11:05 106阅读 0赞

流程控制语句

判断语句

if

主要是判断true /false

  1. int score=80;
  2.         if(score>=80){
  4.             System.out.println("优秀");
  5.         }else if(score>=60){
  7.             System.out.println("及格");
  8.         }else{
  10.             System.out.println("不及格");
  11.         }
switch
  1. int month = 8;
  2.         String monthString;
  3.         switch (month) {
  4.     //switch表达式不能为空
  5.             case 1:  monthString = "January";
  6.                      break;
  7.             case 2:  monthString = "February";
  8.                      break;
  9.             case 3:  monthString = "March";
  10.                      break;
  11.             case 4:  monthString = "April";
  12.                      break;
  13.             case 5:  monthString = "May";
  14.                      break;
  15.             case 6:  monthString = "June";
  16.                      break;
  17.             case 7:  monthString = "July";
  18.                      break;
  19.             case 8:  monthString = "August";
  20.                      break;
  21.             case 9:  monthString = "September";
  22.                      break;
  23.             case 10: monthString = "October";
  24.                      break;
  25.             case 11: monthString = "November";
  26.                      break;
  27.             case 12: monthString = "December";
  28.                      break;
  29.             default: monthString = "Invalid month";
  30.                      break;//最后一个break,不是必须的，但建议写上
  31.         }
  32.         System.out.println(monthString);

循环语句

while
  1. while (expression) {
  3.      statement(s)
  4. }
do…while
  1. do {
  3.      statement(s)
  4. } while (expression);

do语句至少执行一次

for循环
  1. for (initialization; termination;increment) {
  3.     statement(s)
  4. }

initialization表达式初始化循环; 在循环开始时执行一次

termination循环终止条件

increment增量，每次循环最后被调用

增强for循环（推荐）
  1. int[] numbers = 
  2.              {
  3.     1,2,3,4,5,6,7,8,9,10};
  4.          for (int item : numbers) {
  6.              System.out.println("Count is: " + item);
  7.          }

分支语句

break
switch
循环中

跳出循环

跳出内层循环

带标签的break
  1. label://label可以自定义，label1....
  2.         for (int i = 0; i < 3; i++) {
  4.             for (int j = 0; j < 3; j++) {
  6.                 if(j==2){
  8.                     break label;//直接跳出外层循环
  9.                 }
  10.                 System.out.println("内");
  11.             }
  12.             System.out.println("外");
  13.         }
continue

跳过该次循环的剩余部分，继续执行下一次循环

跳过内层循环

带标签的continue

跳过label标签的大循环

  1. label:
  2.         for (int i = 0; i < 3; i++) {
  4.             for (int j = 0; j < 3; j++) {
  6.                 if(j==2){
  8.                    continue label;
  9.                 }
  10.                 System.out.println("内");
  11.             }
  12.             System.out.println("外");
  13.         }
return

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