标签：语言
public static void testBase(int i)
{
i = 2;
}int i = 10; System.out.println(i);//10 testBase(i); System.out.println(i); //10
public static void testObj(Object o)
{
o = new Object();
}Object o = new Object(); System.out.println(o);// java.lang.Object@1ff61bcf testObj(o); System.out.println(o);//java.lang.Object@1ff61bcf
public class S
{
private Object o = new Object();
private int i = 2;
public Object getO()
{
return o;
}
public void setO(Object o)
{
this.o = o;
}
public int getI()
{
return i;
}
public void setI(int i)
{
this.i = i;
}
}
测试方法：public static void testA(S s)
{
s.setI(100);
s.setO(new Object());
}S s = new S(); System.out.println(s.getI()+","+s.getO());// 2,java.lang.Object@11b75be2 testA(s); System.out.println(s.getI()+","+s.getO());//100,java.lang.Object@1cf15b84
package test;
public class A
{
int t = 6;
Object obj = new Object();
public static void main(String[] args)
{
A a = new A();
a.func(a.t,a.obj);//问t和obj的值是否变化，答案：不变化
}
public void func(int t,Object obj)
{
t = 7;
obj = null;
}
}
public static void testArr(int[] arr)
{
arr = null;
}测试：int[] arr = {1,2};
System.out.println(arr[0]);//1
testArr(arr);
System.out.println(arr[0]); //1
public static void testArr(int[] arr)
{
arr[0] = 100;
}测试：int[] arr = {1,2};
System.out.println(arr[0]);//1
testArr(arr);
System.out.println(arr[0]);//100
public static void testWrapper(Float f)
{
f = 100.0f;
}测试：Float f = 12.0f; System.out.println(f);//12.0 testWrapper(f); System.out.println(f);//12.0
public static void testStr1(String str)
{
str = "testOK";
}测试：String str = "test"; System.out.println(str);//test testStr1(str); System.out.println(str);//test根据前面的思路，字符串也是对象，参数拷贝的是对象的地址，在方法内部将参数指向另一个堆对象并不影响原始对象引用的指向。
public static void testStr2(String str)
{
str = str.concat("OK");
str = str.toUpperCase();
}测试：String str = "test"; System.out.println(str);//test testStr2(str); System.out.println(str);//test
public static void testStr3(String str)
{
str += "OK";
}测试：String str = "test"; System.out.println(str);//test testStr3(str); System.out.println(str);//test如果你以为第二次输出testOK，那就错啦，String类的’+‘是经过重载的，编译时会还原成StringBuilder的append操作，并且new了一个StringBuilder对象：
str += "OK";
str = new StringBuilder(str).append("OK").toString();//编译时会还原成这样
public static void testStringBuilder(StringBuilder sb)
{
sb = new StringBuilder("testOK");
} 测试：StringBuilder sb = new StringBuilder("test");
System.out.println(sb.toString());//test
testStringBuilder(sb);
System.out.println(sb.toString());//test 6.2在方法内部调用StringBuffer或StringBuilder的append方法：public static void testStringBuilder(StringBuilder sb)
{
sb.append("OK");
} 测试：StringBuilder sb = new StringBuilder("test");
System.out.println(sb.toString());//test
testStringBuilder(sb);
System.out.println(sb.toString());//testOK
public static void swap(Integer a, Integer b)
{
Integer temp = a;
a = b;
b = temp;
}这根本不能交换两个数.Sdut 2409 The Best Seat in ACM Contest(山东省第三届ACM省赛 H 题)(模拟)
标签：语言
原文地址：http://blog.csdn.net/gray_1566/article/details/24621599
