3、
class Test {
public static void main(String[] args) {
String s1 = "123";
String s2 = "123";
if (s1 == s2) {
System.out.println("s1==s2");
} else {
System.out.println("s1!=s2");
}
}
}
输出结果：s1==s2
|
4、
class Test {
public static void main(String[] args) {
String s1 = new String("123");
String s2 = new String("123");
if (s1 == s2) {
System.out.println("s1==s2");
} else {
System.out.println("s1!=s2");
}
}
}
结果：s1!=s2
|
5、
class Test {
public static void main(String[] args) {
String s1 = new String("123");
String s2 = new String("123");
} } Runtime Heap Summary: Test
========================== Runtime Instance List
--------------------- Package Class Count Cumulative Count Memory Cumulative Memory
------- ----- ----- ---------------- ------ -----------------
Total 4 (100.0%) 4 (100.0%) 96 (100.0%) 96 (100.0%)
java.lang String 3 (75.0%) 3 (75.0%) 72 (75.0%) 72 (75.0%)
char[ ] 1 (25.0%) 1 (25.0%) 24 (25.0%) 24 (25.0%)
|
结论：相同字符串常量，即使在不同语句中被引用，其内存是共用的，"123"只生成一个字符数据和一个String对象，两个new String()分别生成了一个对象。
6、
class Test
{
public static void main(String[] args)
{
String s1 = new String("123");
String s2 = new String("1234");
}
} Runtime Heap Summary: Test
========================== Runtime Instance List
--------------------- Package Class Count Cumulative Count Memory Cumulative Memory
------- ----- ----- ---------------- ------ -----------------
Total 6 (100.0%) 6 (100.0%) 144 (100.0%) 144 (100.0%)
java.lang String 4 (66.7%) 4 (66.7%) 96 (66.7%) 96 (66.7%)
char[ ] 2 (33.3%) 2 (33.3%) 48 (33.3%) 48 (33.3%)
|
结论："123"和"1234"分别生成了各自的字符数组和String对象。两个new String()分别创建一个String对象。
做了一个测试，
long begin = System.nanoTime();
//String str = "abcdefghijklmnopqrstuvwxyz";
String str1 = new String("abcdefghijklmnopqrstuvwxyz");
long end = System.nanoTime();
System.out.println(end - begin);
|
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佚名
2008-5-12
