java运算符总结

下面这个例子向各人展示了如何伴同特定的运算符利用主数据范例。从基础上说，它是同一个例子反重复复地执行，只是利用了差异的主数据范例。文件编译时不会报错，因为那些会导致错误的行已用//!酿成了注释内容。

 

//: 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;
  }
} ///:~

#p#分页标题#e#

留意布尔值（boolean）的本领很是有限。我们只能为其赋予true和false值。并且可测试它为真照旧为假，但不行为它们再添加布尔值，或举办其他其他任何范例运算。
在char，byte和short中，我们可看到算术运算符的“转型”结果。对这些范例的任何一个举办算术运算，城市得到一个int功效。必需将其明晰“造型”回本来的范例（缩小转换会造成信息的丢失），以便将值赋回谁人范例。但对付int值，却不必举办造型处理惩罚，因为所有数据都已经属于int范例。然而，不要放松鉴戒，认为一切工作都是安详的。假如对两个足够大的int值执行乘法运算，功效值就会溢出。下面这个例子向各人展示了这一点：

 

//: 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);
  }
} ///:~

输出功效如下：
big = 2147483647
bigger = -4

并且不会从编译器哪里收到堕落提示，运行时也不会呈现异常回响。爪哇咖啡（Java）确实是很好的对象，但却没有“那么”好！
对付char，byte可能short，殽杂赋值并不需要造型。纵然它们执行转型操纵，也会得到与直接算术运算沟通的功效。而在另一方面，将造型略去可使代码显得越发简洁。
各人可以看到，除boolean以外，任何一种主范例都可通过造型变为其他主范例。同样地，当造型成一种较小的范例时，必需寄望“缩小转换”的效果。不然会在造型进程中不知不觉地丢失信息。