java运算符总结

ㄣ负二代

下面这个例子向大家展示了如何随同特定的运算符使用主数据类型。从根本上说，它是同一个例子反反复复地执行，只是使用了不同的主数据类型。文件编译时不会报错，因为那些会导致错误的行已用//!变成了注释内容。
//: AllOps.java// Tests all the operators on all the// primitive data types to show which// ones are accepted by the Java compiler.class AllOps {  // To accept the results of a boolean test:  void f(boolean b) {}  void boolTest(boolean x, boolean y) {    // Arithmetic operators:    //! x = x * y;    //! x = x / y;    //! x = x % y;    //! x = x + y;    //! x = x - y;    //! x++;    //! x--;    //! x = +y;    //! x = -y;    // Relational and logical:    //! f(x > y);    //! f(x >= y);    //! f(x < y);    //! f(x <= y);    f(x == y);    f(x != y);    f(!y);    x = x && y;    x = x || y;    // Bitwise operators:    //! x = ~y;    x = x & y;    x = x | y;    x = x ^ y;    //! x = x << 1;    //! x = x >> 1;    //! x = x >>> 1;    // Compound assignment:    //! x += y;    //! x -= y;    //! x *= y;    //! x /= y;    //! x %= y;    //! x <<= 1;    //! x >>= 1;    //! x >>>= 1;    x &= y;    x ^= y;    x |= y;    // Casting:    //! char c = (char)x;    //! byte B = (byte)x;    //! short s = (short)x;    //! int i = (int)x;    //! long l = (long)x;    //! float f = (float)x;    //! double d = (double)x;  }  void charTest(char x, char y) {    // Arithmetic operators:    x = (char)(x * y);    x = (char)(x / y);    x = (char)(x % y);    x = (char)(x + y);    x = (char)(x - y);    x++;    x--;    x = (char)+y;    x = (char)-y;    // Relational and logical:    f(x > y);    f(x >= y);    f(x < y);    f(x <= y);    f(x == y);    f(x != y);    //! f(!x);    //! f(x && y);    //! f(x || y);    // Bitwise operators:    x= (char)~y;    x = (char)(x & y);    x  = (char)(x | y);    x = (char)(x ^ y);    x = (char)(x << 1);    x = (char)(x >> 1);    x = (char)(x >>> 1);    // Compound assignment:    x += y;    x -= y;    x *= y;    x /= y;    x %= y;    x <<= 1;    x >>= 1;    x >>>= 1;    x &= y;    x ^= y;    x |= y;    // Casting:    //! boolean b = (boolean)x;    byte B = (byte)x;    short s = (short)x;    int i = (int)x;    long l = (long)x;    float f = (float)x;    double d = (double)x;  }  void byteTest(byte x, byte y) {    // Arithmetic operators:    x = (byte)(x* y);    x = (byte)(x / y);    x = (byte)(x % y);    x = (byte)(x + y);    x = (byte)(x - y);    x++;    x--;    x = (byte)+ y;    x = (byte)- y;    // Relational and logical:    f(x > y);    f(x >= y);    f(x < y);    f(x <= y);    f(x == y);    f(x != y);    //! f(!x);    //! f(x && y);    //! f(x || y);    // Bitwise operators:    x = (byte)~y;    x = (byte)(x & y);    x = (byte)(x | y);    x = (byte)(x ^ y);    x = (byte)(x << 1);    x = (byte)(x >> 1);    x = (byte)(x >>> 1);    // Compound assignment:    x += y;    x -= y;    x *= y;    x /= y;    x %= y;    x <<= 1;    x >>= 1;    x >>>= 1;    x &= y;    x ^= y;    x |= y;    // Casting:    //! boolean b = (boolean)x;    char c = (char)x;    short s = (short)x;    int i = (int)x;    long l = (long)x;    float f = (float)x;    double d = (double)x;  }  void shortTest(short x, short y) {    // Arithmetic operators:    x = (short)(x * y);    x = (short)(x / y);    x = (short)(x % y);    x = (short)(x + y);    x = (short)(x - y);    x++;    x--;    x = (short)+y;    x = (short)-y;    // Relational and logical:    f(x > y);    f(x >= y);    f(x < y);    f(x <= y);    f(x == y);    f(x != y);    //! f(!x);    //! f(x && y);    //! f(x || y);    // Bitwise operators:    x = (short)~y;    x = (short)(x & y);    x = (short)(x | y);    x = (short)(x ^ y);    x = (short)(x << 1);    x = (short)(x >> 1);    x = (short)(x >>> 1);    // Compound assignment:    x += y;    x -= y;    x *= y;    x /= y;    x %= y;    x <<= 1;    x >>= 1;    x >>>= 1;    x &= y;    x ^= y;    x |= y;    // Casting:    //! boolean b = (boolean)x;    char c = (char)x;    byte B = (byte)x;    int i = (int)x;    long l = (long)x;    float f = (float)x;    double d = (double)x;  }  void intTest(int x, int y) {    // Arithmetic operators:    x = x * y;    x = x / y;    x = x % y;    x = x + y;    x = x - y;    x++;    x--;    x = +y;    x = -y;    // Relational and logical:    f(x > y);    f(x >= y);    f(x < y);    f(x <= y);    f(x == y);    f(x != y);    //! f(!x);    //! f(x && y);    //! f(x || y);    // Bitwise operators:    x = ~y;    x = x & y;    x = x | y;    x = x ^ y;    x = x << 1;    x = x >> 1;    x = x >>> 1;    // Compound assignment:    x += y;    x -= y;    x *= y;    x /= y;    x %= y;    x <<= 1;    x >>= 1;    x >>>= 1;    x &= y;    x ^= y;    x |= y;    // Casting:    //! boolean b = (boolean)x;    char c = (char)x;    byte B = (byte)x;    short s = (short)x;    long l = (long)x;    float f = (float)x;    double d = (double)x;  }  void longTest(long x, long y) {    // Arithmetic operators:    x = x * y;    x = x / y;    x = x % y;    x = x + y;    x = x - y;    x++;    x--;    x = +y;    x = -y;    // Relational and logical:    f(x > y);    f(x >= y);    f(x < y);    f(x <= y);    f(x == y);    f(x != y);    //! f(!x);    //! f(x && y);    //! f(x || y);    // Bitwise operators:    x = ~y;    x = x & y;    x = x | y;    x = x ^ y;    x = x << 1;    x = x >> 1;    x = x >>> 1;    // Compound assignment:    x += y;    x -= y;    x *= y;    x /= y;    x %= y;    x <<= 1;    x >>= 1;    x >>>= 1;    x &= y;    x ^= y;    x |= y;    // Casting:    //! boolean b = (boolean)x;    char c = (char)x;    byte B = (byte)x;    short s = (short)x;    int i = (int)x;    float f = (float)x;    double d = (double)x;  }  void floatTest(float x, float y) {    // Arithmetic operators:    x = x * y;    x = x / y;    x = x % y;    x = x + y;    x = x - y;    x++;    x--;    x = +y;    x = -y;    // Relational and logical:    f(x > y);    f(x >= y);    f(x < y);    f(x <= y);    f(x == y);    f(x != y);    //! f(!x);    //! f(x && y);    //! f(x || y);    // Bitwise operators:    //! x = ~y;    //! x = x & y;    //! x = x | y;    //! x = x ^ y;    //! x = x << 1;    //! x = x >> 1;    //! x = x >>> 1;    // Compound assignment:    x += y;    x -= y;    x *= y;    x /= y;    x %= y;    //! x <<= 1;    //! x >>= 1;    //! x >>>= 1;    //! x &= y;    //! x ^= y;    //! x |= y;    // Casting:    //! boolean b = (boolean)x;    char c = (char)x;    byte B = (byte)x;    short s = (short)x;    int i = (int)x;    long l = (long)x;    double d = (double)x;  }  void doubleTest(double x, double y) {    // Arithmetic operators:    x = x * y;    x = x / y;    x = x % y;    x = x + y;    x = x - y;    x++;    x--;    x = +y;    x = -y;    // Relational and logical:    f(x > y);    f(x >= y);    f(x < y);    f(x <= y);    f(x == y);    f(x != y);    //! f(!x);    //! f(x && y);    //! f(x || y);    // Bitwise operators:    //! x = ~y;    //! x = x & y;    //! x = x | y;    //! x = x ^ y;    //! x = x << 1;    //! x = x >> 1;    //! x = x >>> 1;    // Compound assignment:    x += y;    x -= y;    x *= y;    x /= y;    x %= y;    //! x <<= 1;    //! x >>= 1;    //! x >>>= 1;    //! x &= y;    //! x ^= y;    //! x |= y;    // Casting:    //! boolean b = (boolean)x;    char c = (char)x;    byte B = (byte)x;    short s = (short)x;    int i = (int)x;    long l = (long)x;    float f = (float)x;  }} ///:~
注意布尔值（boolean）的能力非常有限。我们只能为其赋予true和false值。而且可测试它为真还是为假，但不可为它们再添加布尔值，或进行其他其他任何类型运算。
在char，byte和short中，我们可看到算术运算符的“转型”效果。对这些类型的任何一个进行算术运算，都会获得一个int结果。必须将其明确“造型”回原来的类型（缩小转换会造成信息的丢失），以便将值赋回那个类型。但对于int值，却不必进行造型处理，因为所有数据都已经属于int类型。然而，不要放松警惕，认为一切事情都是安全的。如果对两个足够大的int值执行乘法运算，结果值就会溢出。下面这个例子向大家展示了这一点：

//: Overflow.java// Surprise! Java lets you overflow.public class Overflow {  public static void main(String[] args) {    int big = 0x7fffffff; // max int value    prt("big = " + big);    int bigger = big * 4;    prt("bigger = " + bigger);  }  static void prt(String s) {    System.out.println(s);  }} ///:~

输出结果如下：
big = 2147483647
bigger = -4

而且不会从编译器那里收到出错提示，运行时也不会出现异常反应。爪哇咖啡（Java）确实是很好的东西，但却没有“那么”好！
对于char，byte或者short，混合赋值并不需要造型。即使它们执行转型操作，也会获得与直接算术运算相同的结果。而在另一方面，将造型略去可使代码显得更加简练。
大家可以看到，除boolean以外，任何一种主类型都可通过造型变为其他主类型。同样地，当造型成一种较小的类型时，必须留意“缩小转换”的后果。否则会在造型过程中不知不觉地丢失信息。