✔《Java编程思想》（第4版）第2章 习题

练习1

public class Test {
    static int a;
    static char b;

    public static void main(String[] args) {

        System.out.println("a: " + a);
        System.out.println("b: " + b);
    }
    
}

练习2

public class Test {

    public static void main(String[] args) {

        System.out.println("Hello, World!");
    }

}

练习3

public class Test {

    public static void main(String[] args) {

        ATypeName name = new ATypeName();
        System.out.println(name.a);
    }

}

class ATypeName {
    public int a = 123;
}

练习4

public class Test {

    public static void main(String[] args) {

        DataOnly only = new DataOnly();
        System.out.println(only.a + only.b);
    }

}

class DataOnly {
    int a = 123;
    int b = 321;
}

练习5

public class Test {

    public static void main(String[] args) {

        DataOnly only = new DataOnly();
        System.out.println(only.a + only.b);
    }

}

class DataOnly {
    int a = 2;
    int b = 4;
}

练习6

public class Test {

    public static void main(String[] args) {
        Test test = new Test();
        System.out.println(test.storage("abc"));
    }

    public int storage(String s) {
        return s.length() * 2;
    }
}

练习7

public class Test {

    public static void main(String[] args) {
        System.out.println("i: " + StaticTest.i);
        Incrementable.increment();
        System.out.println("i: " + StaticTest.i);
    }

}

class StaticTest {
    static int i = 47;
}

class Incrementable {
    static void increment() {
        StaticTest.i++;
    }
}

练习8

public class Test {
    static int a = 100;

    public static void main(String[] args) {
        Test test1 = new Test();
        Test test2 = new Test();
        Test test3 = new Test();

        System.out.println("a: " + a);
        test1.a--;
        test2.a--;
        System.out.println("a: " + a);
    }

}

练习9

public class Test {

    public static void main(String[] args) {
        boolean b = true;
        System.out.println("boolean b: " + b);
        Boolean B = b;
        System.out.println("Boolean B: " + B);

        char c = 'a';
        System.out.println("char c: " + c);
        Character C = c;
        System.out.println("Character C: " + C);

        byte t = 9;
        System.out.println("byte t: " + t);
        Byte T = t;
        System.out.println("Byte T: " + T);

        short s = 15;
        System.out.println("short s: " + s);
        Short S = s;
        System.out.println("Short S: " + S);

        int i = 99;
        System.out.println("int i: " + i);
        Integer I = i;
        System.out.println("Integer I: " + I);

        long l = 10101;
        System.out.println("long l: " + l);
        Long L = l;
        System.out.println("Long L: " + L);

        float f = 0.3244f;
        System.out.println("float f: " + f);
        Float F = f;
        System.out.println("Float F: " + F);

        double d = 0.6432;
        System.out.println("double d: " + d);
        Double D = d;
        System.out.println("Double D: " + D);
    }

}

练习10

public class Test {

    public static void main(String[] args) {
        for (String s : args)
            System.out.println(s);
    }
}

练习11

public class Test {

    public static void main(String[] args) {
        AllTheColorsOfTheRainbow cc = new AllTheColorsOfTheRainbow();
        cc.changeTheHueOfTheColor(cc.anIntegerRepresentingColors);
    }
}

class AllTheColorsOfTheRainbow {
    int anIntegerRepresentingColors;

    void changeTheHueOfTheColor(int newHue) {
        System.out.println(newHue);
    }
}