日期:2011-03-22 16:17:00 来源:本站整理
<b>java运算符总结</b>[Java编程]
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下面这个例子向大家展示了若何伴随特定的运算符利用主数据范例.从根本上说,它是同一个例子反反复复地履行,只是利用了差别的主数据范例.文件编译时不会报错,因为那些会招致错误的行已用//!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)的本领非常有限.我们只能为其赋予true和false值.并且可测试它为真还是为假,但不可为它们再增添布尔值,或举行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”效果.对这些范例的任何一个举行算术运算,城市得到一个int后果.必须将其明确“造型”回本来的范例(缩小转换会造成信息的丧失),以便将值赋回那个范例.但关于int值,却没必要举行造型处理,因为全部数据都已经属于int范例.但是,不要放松鉴戒,认为一切事情都是安全的.假如对两个充足大的int值履行乘法运算,后果值就会溢出.下面这个例子向大家展示了这一点:
输出后果以下://: 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); } } ///:~
big = 2147483647
bigger = -4
并且不会从编译器那边收到出错提醒,运行时也不会呈现非常反映.爪哇咖啡(Java)确切是很好的东西,但却没有“那么”好!
关于char,byte大概short,混合赋值并不需求造型.即便它们履行转型操作,也会得到与直接算术运算相同的后果.而在另一方面,将造型略去可以使代码显得越发简洁.
大家可以看到,除boolean以外,任何一种主范例都可通过造型变成其他主范例.一样地,当造型成一种较小的范例时,必须留神“缩小转换”的后果.不然会在造型历程中不知不觉地丧失信息.
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