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12-操作符和数据类型总结

AI悦创原创Java体系课Java体系课大约 9 分钟...约 2582 字

0. 目录

  • 自增和自减操作符
  • 打印 26 个连续的字符
  • 找到可以被整除的数

1. 自增和自减操作符

  • 自增自减操作符是可以直接改变变量值的操作符
  • 前加加和前减减
  • 后加加和后减减
  • ++：其实是一个 +1 操作和一个赋值操作的缩写
  • --：其实是一个 -1 操作和一个赋值操作的缩写
public class IncreaseDecrease {
    public static void main(String[] args) {
        int a = 1;
        System.out.println("a++=" + a++);  // a++=1
        System.out.println("a=" + a);   // a=2
        /*等价于：
         * int a = 1;
         * System.out.println("a++=" + a);
         * a = a + 1; // or a += 1;
         * System.out.println("a=" + a);
         * */


        int b = 10;
        System.out.println("b--=" + b--);  // b--=10
        System.out.println("b=" + b);  // b=9

    }
}

输出：

a++=1
a=2
b--=10
b=9

前加加、后加加代码一起来实现一下：

public class IncreaseDecrease2 {
    public static void main(String[] args) {
        int a = 1;
        System.out.println("a++=" + a++);  // a++=1
        System.out.println("a=" + a);  // a=2
        a = 1;
        System.out.println("++a=" + (++a));  // ++a=2
//        System.out.println("++a=" + ++a);  // ++a=2
        System.out.println("a=" + a);  // a=2


        int b = 10;
        System.out.println("b--=" + b--);  // b--=10
        System.out.println("b=" + b);   // b=9

        b = 10;
        System.out.println("--b=" + --b);  // --b=9
        System.out.println("b=" + b);  // b=9
    }
}

分解动作：

public class IncreaseDecrease3 {
    public static void main(String[] args) {
        int a = 1;
        System.out.println("a++=" + a++);

        System.out.println("a++=" + a);
        a = a + 1;

        a = 1;

        System.out.println("++a=" + (++a));

        a = a + 1;
        System.out.println("++a=" + a);
    }
}

2. 打印 26 个连续的字符

2.1 程序中的知识点

  • 自动类型转换：char 到 int「int num = ch;」
  • 强制类型转换：int 到 char 「(char) num++)」
  • 字符和数字的对应关系，字符集和编码
  • 字符串的加法：任何数据和字符串都可以相加，将这个数据的字符串和另一个字符串拼接起来。
  • 自增操作符
public class Print26Chars {
    public static void main(String[] args) {
        char ch = 'A';
        int num = ch;
        System.out.println(num + "\t" + ((char) num++));
        System.out.println(num + "\t" + ((char) num++));
        System.out.println(num + "\t" + ((char) num++));
        System.out.println(num + "\t" + ((char) num++));
        System.out.println(num + "\t" + ((char) num++));
        System.out.println(num + "\t" + ((char) num++));
        System.out.println(num + "\t" + ((char) num++));
        System.out.println(num + "\t" + ((char) num++));
        System.out.println(num + "\t" + ((char) num++));
        System.out.println(num + "\t" + ((char) num++));
        System.out.println(num + "\t" + ((char) num++));
        System.out.println(num + "\t" + ((char) num++));
        System.out.println(num + "\t" + ((char) num++));
        System.out.println(num + "\t" + ((char) num++));
        System.out.println(num + "\t" + ((char) num++));
        System.out.println(num + "\t" + ((char) num++));
        System.out.println(num + "\t" + ((char) num++));
        System.out.println(num + "\t" + ((char) num++));
        System.out.println(num + "\t" + ((char) num++));
        System.out.println(num + "\t" + ((char) num++));
        System.out.println(num + "\t" + ((char) num++));
        System.out.println(num + "\t" + ((char) num++));
        System.out.println(num + "\t" + ((char) num++));
        System.out.println(num + "\t" + ((char) num++));
        System.out.println(num + "\t" + ((char) num++));
        System.out.println(num + "\t" + ((char) num++));

    }
}

下面这种方法，有风险，还是建议使用下面的最后一行代码。

public class demo {
    public static void main(String[] args) {
        char ch = 'a';
        System.out.println(ch++);
        System.out.println(ch++);
        System.out.println(ch++);
        System.out.println(ch++);
        System.out.println(ch++);
        System.out.println(ch++);
        System.out.println(ch++);
        System.out.println(ch++);
        System.out.println(ch++);
        System.out.println(ch++);
        System.out.println(ch++);
        System.out.println(ch++);
        System.out.println(ch++);
        System.out.println(ch++);
        System.out.println(ch++);
        System.out.println(ch++);
        System.out.println(ch++);
        System.out.println(ch++);
        System.out.println(ch++);
        System.out.println(ch++);
        System.out.println(ch++);
        System.out.println(ch++);
        System.out.println(ch++);
        System.out.println(ch++);
        System.out.println(ch++);
        System.out.println((char)(ch++));
    }
}
  1. 如果把 ++ 放在前面，会怎么样呢？
  2. 如果去掉 int 会怎么样呢？
public class Print26Chars2 {
    public static void main(String[] args) {
        char ch = 'A';
        int num = ch;
        System.out.println(num + "\t" + (num++));
        System.out.println(num + "\t" + (num++));
        System.out.println(num + "\t" + (num++));
        System.out.println(num + "\t" + (num++));
        System.out.println(num + "\t" + (num++));
        System.out.println(num + "\t" + (num++));
        System.out.println(num + "\t" + (num++));
        System.out.println(num + "\t" + (num++));
        System.out.println(num + "\t" + (num++));
        System.out.println(num + "\t" + (num++));
        System.out.println(num + "\t" + (num++));
        System.out.println(num + "\t" + (num++));
        System.out.println(num + "\t" + (num++));
        System.out.println(num + "\t" + (num++));
        System.out.println(num + "\t" + (num++));
        System.out.println(num + "\t" + (num++));
        System.out.println(num + "\t" + (num++));
        System.out.println(num + "\t" + (num++));
        System.out.println(num + "\t" + (num++));
        System.out.println(num + "\t" + (num++));
        System.out.println(num + "\t" + (num++));
        System.out.println(num + "\t" + (num++));
        System.out.println(num + "\t" + (num++));
        System.out.println(num + "\t" + (num++));
        System.out.println(num + "\t" + (num++));
        System.out.println(num + "\t" + (num++));

    }
}

输出：

/Library/Java/JavaVirtualMachines/jdk-14.0.1.jdk/Contents/Home/bin/java -javaagent:/Applications/IntelliJ IDEA CE.app/Contents/lib/idea_rt.jar=49993:/Applications/IntelliJ IDEA CE.app/Contents/bin -Dfile.encoding=UTF-8 -classpath /Users/apple/Desktop/GitHub/Java_Coder/Coder12/out/production/Coder12 Print26Chars2
65	65
66	66
67	67
68	68
69	69
70	70
71	71
72	72
73	73
74	74
75	75
76	76
77	77
78	78
79	79
80	80
81	81
82	82
83	83
84	84
85	85
86	86
87	87
88	88
89	89
90	90

Process finished with exit code 0

测试 unicode 的代码：

public class Print26Chars3 {
    public static void main(String[] args) {
        char ch = '\u1234';
        // char ch = '\u5234';
        int num = ch;
        System.out.println(num + "\t" + ((char) num++));
        System.out.println(num + "\t" + ((char) num++));
        System.out.println(num + "\t" + ((char) num++));
        System.out.println(num + "\t" + ((char) num++));
        System.out.println(num + "\t" + ((char) num++));
        System.out.println(num + "\t" + ((char) num++));
        System.out.println(num + "\t" + ((char) num++));
        System.out.println(num + "\t" + ((char) num++));
        System.out.println(num + "\t" + ((char) num++));
        System.out.println(num + "\t" + ((char) num++));
        System.out.println(num + "\t" + ((char) num++));
        System.out.println(num + "\t" + ((char) num++));
        System.out.println(num + "\t" + ((char) num++));
        System.out.println(num + "\t" + ((char) num++));
        System.out.println(num + "\t" + ((char) num++));
        System.out.println(num + "\t" + ((char) num++));
        System.out.println(num + "\t" + ((char) num++));
        System.out.println(num + "\t" + ((char) num++));
        System.out.println(num + "\t" + ((char) num++));
        System.out.println(num + "\t" + ((char) num++));
        System.out.println(num + "\t" + ((char) num++));
        System.out.println(num + "\t" + ((char) num++));
        System.out.println(num + "\t" + ((char) num++));
        System.out.println(num + "\t" + ((char) num++));
        System.out.println(num + "\t" + ((char) num++));
        System.out.println(num + "\t" + ((char) num++));

    }
}

输出：

/Library/Java/JavaVirtualMachines/jdk-14.0.1.jdk/Contents/Home/bin/java -javaagent:/Applications/IntelliJ IDEA CE.app/Contents/lib/idea_rt.jar=54697:/Applications/IntelliJ IDEA CE.app/Contents/bin -Dfile.encoding=UTF-8 -classpath /Users/apple/Desktop/GitHub/Java_Coder/Coder12/out/production/Coder12 Print26Chars3
4660	ሴ
4661	ስ
4662	ሶ
4663	ሷ
4664	ሸ
4665	ሹ
4666	ሺ
4667	ሻ
4668	ሼ
4669	ሽ
4670	ሾ
4671	ሿ
4672	ቀ
4673	ቁ
4674	ቂ
4675	ቃ
4676	ቄ
4677	ቅ
4678	ቆ
4679	ቇ
4680	ቈ
4681	቉
4682	ቊ
4683	ቋ
4684	ቌ
4685	ቍ

Process finished with exit code 0

3. 找到可以被整除的数

3.1 程序中的知识点

  • 取模运算：整数的取模运算
  • 布尔运算：== 操作符
  • 自增运算
public class FindDiv {
    public static void main(String[] args) {
        int dividend = 35;
        int divisor = 9;
        System.out.println(dividend + "可以整除" + divisor + "吗？" + ((dividend++) % divisor == 0));
        System.out.println(dividend + "可以整除" + divisor + "吗？" + ((dividend++) % divisor == 0));
        System.out.println(dividend + "可以整除" + divisor + "吗？" + ((dividend++) % divisor == 0));
        System.out.println(dividend + "可以整除" + divisor + "吗？" + ((dividend++) % divisor == 0));
        System.out.println(dividend + "可以整除" + divisor + "吗？" + ((dividend++) % divisor == 0));
        System.out.println(dividend + "可以整除" + divisor + "吗？" + ((dividend++) % divisor == 0));
        System.out.println(dividend + "可以整除" + divisor + "吗？" + ((dividend++) % divisor == 0));
        System.out.println(dividend + "可以整除" + divisor + "吗？" + ((dividend++) % divisor == 0));
        System.out.println(dividend + "可以整除" + divisor + "吗？" + ((dividend++) % divisor == 0));
        System.out.println(dividend + "可以整除" + divisor + "吗？" + ((dividend++) % divisor == 0));
        System.out.println(dividend + "可以整除" + divisor + "吗？" + ((dividend++) % divisor == 0));
        System.out.println(dividend + "可以整除" + divisor + "吗？" + ((dividend++) % divisor == 0));
        System.out.println(dividend + "可以整除" + divisor + "吗？" + ((dividend++) % divisor == 0));
        System.out.println(dividend + "可以整除" + divisor + "吗？" + ((dividend++) % divisor == 0));
        System.out.println(dividend + "可以整除" + divisor + "吗？" + ((dividend++) % divisor == 0));
        System.out.println(dividend + "可以整除" + divisor + "吗？" + ((dividend++) % divisor == 0));
        System.out.println(dividend + "可以整除" + divisor + "吗？" + ((dividend++) % divisor == 0));
        System.out.println(dividend + "可以整除" + divisor + "吗？" + ((dividend++) % divisor == 0));
        System.out.println(dividend + "可以整除" + divisor + "吗？" + ((dividend++) % divisor == 0));
        System.out.println(dividend + "可以整除" + divisor + "吗？" + ((dividend++) % divisor == 0));
        System.out.println(dividend + "可以整除" + divisor + "吗？" + ((dividend++) % divisor == 0));
        System.out.println(dividend + "可以整除" + divisor + "吗？" + ((dividend++) % divisor == 0));
        System.out.println(dividend + "可以整除" + divisor + "吗？" + ((dividend++) % divisor == 0));
        System.out.println(dividend + "可以整除" + divisor + "吗？" + ((dividend++) % divisor == 0));
        System.out.println(dividend + "可以整除" + divisor + "吗？" + ((dividend++) % divisor == 0));
        System.out.println(dividend + "可以整除" + divisor + "吗？" + ((dividend++) % divisor == 0));
        System.out.println(dividend + "可以整除" + divisor + "吗？" + ((dividend++) % divisor == 0));
        System.out.println(dividend + "可以整除" + divisor + "吗？" + ((dividend++) % divisor == 0));
        System.out.println(dividend + "可以整除" + divisor + "吗？" + ((dividend++) % divisor == 0));
        System.out.println(dividend + "可以整除" + divisor + "吗？" + ((dividend++) % divisor == 0));
        System.out.println(dividend + "可以整除" + divisor + "吗？" + ((dividend++) % divisor == 0));
        System.out.println(dividend + "可以整除" + divisor + "吗？" + ((dividend++) % divisor == 0));
        System.out.println(dividend + "可以整除" + divisor + "吗？" + ((dividend++) % divisor == 0));
        System.out.println(dividend + "可以整除" + divisor + "吗？" + ((dividend++) % divisor == 0));
        System.out.println(dividend + "可以整除" + divisor + "吗？" + ((dividend++) % divisor == 0));
        System.out.println(dividend + "可以整除" + divisor + "吗？" + ((dividend++) % divisor == 0));
        System.out.println(dividend + "可以整除" + divisor + "吗？" + ((dividend++) % divisor == 0));
        System.out.println(dividend + "可以整除" + divisor + "吗？" + ((dividend++) % divisor == 0));
        System.out.println(dividend + "可以整除" + divisor + "吗？" + ((dividend++) % divisor == 0));
        System.out.println(dividend + "可以整除" + divisor + "吗？" + ((dividend++) % divisor == 0));
        System.out.println(dividend + "可以整除" + divisor + "吗？" + ((dividend++) % divisor == 0));
        System.out.println(dividend + "可以整除" + divisor + "吗？" + ((dividend++) % divisor == 0));
        System.out.println(dividend + "可以整除" + divisor + "吗？" + ((dividend++) % divisor == 0));
        System.out.println(dividend + "可以整除" + divisor + "吗？" + ((dividend++) % divisor == 0));
        System.out.println(dividend + "可以整除" + divisor + "吗？" + ((dividend++) % divisor == 0));
        System.out.println(dividend + "可以整除" + divisor + "吗？" + ((dividend++) % divisor == 0));
        System.out.println(dividend + "可以整除" + divisor + "吗？" + ((dividend++) % divisor == 0));
        System.out.println(dividend + "可以整除" + divisor + "吗？" + ((dividend++) % divisor == 0));
        System.out.println(dividend + "可以整除" + divisor + "吗？" + ((dividend++) % divisor == 0));
        System.out.println(dividend + "可以整除" + divisor + "吗？" + ((dividend++) % divisor == 0));
        System.out.println(dividend + "可以整除" + divisor + "吗？" + ((dividend++) % divisor == 0));
        System.out.println(dividend + "可以整除" + divisor + "吗？" + ((dividend++) % divisor == 0));
        System.out.println(dividend + "可以整除" + divisor + "吗？" + ((dividend++) % divisor == 0));
        System.out.println(dividend + "可以整除" + divisor + "吗？" + ((dividend++) % divisor == 0));
        System.out.println(dividend + "可以整除" + divisor + "吗？" + ((dividend++) % divisor == 0));
        System.out.println(dividend + "可以整除" + divisor + "吗？" + ((dividend++) % divisor == 0));
        System.out.println(dividend + "可以整除" + divisor + "吗？" + ((dividend++) % divisor == 0));
        System.out.println(dividend + "可以整除" + divisor + "吗？" + ((dividend++) % divisor == 0));
        System.out.println(dividend + "可以整除" + divisor + "吗？" + ((dividend++) % divisor == 0));
        System.out.println(dividend + "可以整除" + divisor + "吗？" + ((dividend++) % divisor == 0));
        System.out.println(dividend + "可以整除" + divisor + "吗？" + ((dividend++) % divisor == 0));
        System.out.println(dividend + "可以整除" + divisor + "吗？" + ((dividend++) % divisor == 0));
        System.out.println(dividend + "可以整除" + divisor + "吗？" + ((dividend++) % divisor == 0));
        System.out.println(dividend + "可以整除" + divisor + "吗？" + ((dividend++) % divisor == 0));
        System.out.println(dividend + "可以整除" + divisor + "吗？" + ((dividend++) % divisor == 0));
        System.out.println(dividend + "可以整除" + divisor + "吗？" + ((dividend++) % divisor == 0));
        System.out.println(dividend + "可以整除" + divisor + "吗？" + ((dividend++) % divisor == 0));
        System.out.println(dividend + "可以整除" + divisor + "吗？" + ((dividend++) % divisor == 0));
        System.out.println(dividend + "可以整除" + divisor + "吗？" + ((dividend++) % divisor == 0));
        System.out.println(dividend + "可以整除" + divisor + "吗？" + ((dividend++) % divisor == 0));
        System.out.println(dividend + "可以整除" + divisor + "吗？" + ((dividend++) % divisor == 0));
        System.out.println(dividend + "可以整除" + divisor + "吗？" + ((dividend++) % divisor == 0));
        System.out.println(dividend + "可以整除" + divisor + "吗？" + ((dividend++) % divisor == 0));
        System.out.println(dividend + "可以整除" + divisor + "吗？" + ((dividend++) % divisor == 0));
        System.out.println(dividend + "可以整除" + divisor + "吗？" + ((dividend++) % divisor == 0));
        System.out.println(dividend + "可以整除" + divisor + "吗？" + ((dividend++) % divisor == 0));
        System.out.println(dividend + "可以整除" + divisor + "吗？" + ((dividend++) % divisor == 0));
        System.out.println(dividend + "可以整除" + divisor + "吗？" + ((dividend++) % divisor == 0));
        System.out.println(dividend + "可以整除" + divisor + "吗？" + ((dividend++) % divisor == 0));
        System.out.println(dividend + "可以整除" + divisor + "吗？" + ((dividend++) % divisor == 0));
        System.out.println(dividend + "可以整除" + divisor + "吗？" + ((dividend++) % divisor == 0));
        System.out.println(dividend + "可以整除" + divisor + "吗？" + ((dividend++) % divisor == 0));
        System.out.println(dividend + "可以整除" + divisor + "吗？" + ((dividend++) % divisor == 0));
        System.out.println(dividend + "可以整除" + divisor + "吗？" + ((dividend++) % divisor == 0));
        System.out.println(dividend + "可以整除" + divisor + "吗？" + ((dividend++) % divisor == 0));
        System.out.println(dividend + "可以整除" + divisor + "吗？" + ((dividend++) % divisor == 0));
        System.out.println(dividend + "可以整除" + divisor + "吗？" + ((dividend++) % divisor == 0));
        System.out.println(dividend + "可以整除" + divisor + "吗？" + ((dividend++) % divisor == 0));
        System.out.println(dividend + "可以整除" + divisor + "吗？" + ((dividend++) % divisor == 0));
        System.out.println(dividend + "可以整除" + divisor + "吗？" + ((dividend++) % divisor == 0));
        System.out.println(dividend + "可以整除" + divisor + "吗？" + ((dividend++) % divisor == 0));
        System.out.println(dividend + "可以整除" + divisor + "吗？" + ((dividend++) % divisor == 0));
        System.out.println(dividend + "可以整除" + divisor + "吗？" + ((dividend++) % divisor == 0));
        System.out.println(dividend + "可以整除" + divisor + "吗？" + ((dividend++) % divisor == 0));
        System.out.println(dividend + "可以整除" + divisor + "吗？" + ((dividend++) % divisor == 0));
        System.out.println(dividend + "可以整除" + divisor + "吗？" + ((dividend++) % divisor == 0));
        System.out.println(dividend + "可以整除" + divisor + "吗？" + ((dividend++) % divisor == 0));
        System.out.println(dividend + "可以整除" + divisor + "吗？" + ((dividend++) % divisor == 0));
        System.out.println(dividend + "可以整除" + divisor + "吗？" + ((dividend++) % divisor == 0));
        System.out.println(dividend + "可以整除" + divisor + "吗？" + ((dividend++) % divisor == 0));
    }
}

上面写的代码，你会觉得太累了，重复性太强了，就算有快捷复制也会很累的。不要着急，后面会学习到更简便的方法。

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方法一：QQopen in new window

方法二：微信：Jiabcdefh

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贡献者: AndersonHJB
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