04.循环

# 01.if else

# 1、if else

package com.case_01;

public class Test{
    public static void main(String args[]){
        int x = 30;
        int y = 10;

        if( x == 30 ){
            if( y == 10 ){
                System.out.println("X = 30 and Y = 10");
            }
            if (y < 10) {
                System.out.println("c");
            } else if (y < 20) {
                System.out.println("java");
            } else {
                System.out.println("python");
            }
        }
    }
}

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# 2、三元运算

package com.case_01;

public class Test{
    public static void main(String args[]){
        int time = 20;
        String result = (time < 18) ? "学习python" : "学习java";
        System.out.println(result);   // 学习java
    }
}

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# 02.switch 语句

package com.case_01;

public class Test{
    public static void main(String args[]){
        int day = 4;
        switch (day) {
            case 1:
                System.out.println("Monday");
                break;
            case 2:
                System.out.println("Tuesday");
                break;
            case 3:
                System.out.println("Wednesday");
                break;
            case 4:
                System.out.println("Thursday");
                break;
            case 5:
                System.out.println("Friday");
                break;
            case 6:
                System.out.println("Saturday");
                break;
            case 7:
                System.out.println("Sunday");
                break;
            default:
                System.out.println("没有匹配");
        }
        // 输出 "Thursday" (day = 4)
    }
}

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# 03.while 循环

# 1、简单循环

int i = 0;
while (i < 5) {
    System.out.println(i);
    i++;
}

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# 2、do while

do while循环是while循环的变体。
在检查条件是否为true之前，此循环将执行一次代码块，然后只要条件为true，它将重复该循环。

do {
  // 要执行的代码块
}
while (condition);

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public class Test{
    public static void main(String args[]){
        int i = 0;
        do {
            System.out.println(i);
            i++;
        }
        while (i < 5);
    }
}

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# 3、break

public class Test{
    public static void main(String args[]){
        int i = 0;
        while(i <= 100) {
            i++;
            if (i > 30) {
                System.out.println(i + "已经超过了30，不能在循环了");
                break;
            }
        }
    }
}

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# 4、continue

public class Test{
    public static void main(String args[]){
        int i = 0;
        while(i < 100){
            i++;
            if(i%10 == 0){
                System.out.println();
                continue;
            }
            System.out.print(i);
        }
    }
}

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# 04.for循环

# 1、for

此示例将只输出0到10之间的偶数：

for (int i = 0; i <= 10; i = i + 2) {
  System.out.println(i);
}

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# 2、for-each

以下示例使用for-each循环输出angs数组中的所有元素

public class Test{
    public static void main(String args[]){
        String[] langs = {"c", "java", "python", "cjavapy"};
        for (String i : langs) {
            System.out.println(i);
        }
    }
}

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# 3、break

for (int i = 0; i < 10; i++) {
  if (i == 4) {
    break;
  }
  System.out.println(i);
}

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# 4、continue

for (int i = 0; i < 10; i++) {
  if (i == 4) {
    continue;
  }
  System.out.println(i);
}

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上次更新: 2024/5/31 11:18:42

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