Java极简入门之表达式

If 表达式

  • 语法 
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    if (condition) {
    // block of code to be executed if the condition is true
    }
  • 示例 
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    if (20 > 18) {
    System.out.println("20 is greater than 18");
    }

    Switch

  • 语法 
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    switch(expression) {
    case x:
        // code block
        break;
    case y:
        // code block
        break;
    default:
        // code block
    }
  • 示例 
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    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;
    }
    // Outputs "Thursday" (day 4)

While Loop

  • 语法 
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    while (condition) {
        // code block to be executed
    }
  • 示例 
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    int i = 0;
    while (i < 5) {
        System.out.println(i);
        i++;
    }

    Do/While Loop

  • 语法 
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    do {
        // code block to be executed
    }
    while (condition);
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    int i = 0;
    do {
        System.out.println(i);
        i++;
    }
    while (i < 5);

    For Loop

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    for (statement 1; statement 2; statement 3) {
        // code block to be executed
    }
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    for (int i = 0; i < 5; i++) {
        System.out.println(i);
    }

    For-Each Loop

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    for (type variableName : arrayName) {
        // code block to be executed
    }
  • 示例 
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    String[] cars = {"Volvo", "BMW", "Ford", "Mazda"};
    for (String i : cars) {
        System.out.println(i);
    }

    Break

  • break用来“跳出”一条switch语句。
  • break语句还可以用于跳出 循环
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    for (int i = 0; i < 10; i++) {
      if (i == 4) {
        break;
      }
      System.out.println(i);
    }

Continue

continue如果出现指定条件，该语句将中断一次迭代（在循环中），并在循环中继续进行下一次迭代

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