【Java基础】流程控制语句

怼烎@ 2024-03-26 11:05 17阅读 0赞

### 流程控制语句 ###

#### 判断语句 ####

##### if #####

主要是判断true /false

int score=80;
            if(score>=80){
        
                System.out.println("优秀");
            }else if(score>=60){
        
                System.out.println("及格");
            }else{
        
                System.out.println("不及格");
            }

##### switch #####

int month = 8;
            String monthString;
            switch (month) {
        //switch表达式不能为空
                case 1:  monthString = "January";
                         break;
                case 2:  monthString = "February";
                         break;
                case 3:  monthString = "March";
                         break;
                case 4:  monthString = "April";
                         break;
                case 5:  monthString = "May";
                         break;
                case 6:  monthString = "June";
                         break;
                case 7:  monthString = "July";
                         break;
                case 8:  monthString = "August";
                         break;
                case 9:  monthString = "September";
                         break;
                case 10: monthString = "October";
                         break;
                case 11: monthString = "November";
                         break;
                case 12: monthString = "December";
                         break;
                default: monthString = "Invalid month";
                         break;//最后一个break,不是必须的，但建议写上
            }
            System.out.println(monthString);

#### 循环语句 ####

##### while #####

while (expression) {
        
         statement(s)
    }

##### do…while #####

do {
        
         statement(s)
    } while (expression);

do语句至少执行一次

##### for循环 #####

for (initialization; termination;increment) {
        
        statement(s)
    }

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） #####

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

#### 分支语句 ####

##### break #####

###### switch ######

###### 循环中 ######

跳出循环

跳出内层循环

###### 带标签的break ######

label://label可以自定义，label1....
            for (int i = 0; i < 3; i++) {
        
                for (int j = 0; j < 3; j++) {
        
                    if(j==2){
        
                        break label;//直接跳出外层循环
                    }
                    System.out.println("内");
                }
                System.out.println("外");
            }

##### 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

label:
            for (int i = 0; i < 3; i++) {
        
                for (int j = 0; j < 3; j++) {
        
                    if(j==2){
        
                       continue label;
                    }
                    System.out.println("内");
                }
                System.out.println("外");
            }

##### return #####