很全的java.lang.String学习哦 来者给分(没分也学习了）

package linhui1;
public class P3 { /**
 * @param args
 */
public static void main(String[] args) {
// TODO Auto-generated method stub
String s1 = "welcome to java";
String s2=s1;
String s3=new String("welcome to java");
String s4=s3.intern();
System.out.println(s1==s2);//1
System.out.println(s1==s3);//2
System.out.println(s1.equals(s2));//3
System.out.println(s2.equals(s3));//4
System.out.println(s1.compareTo(s2));//5
System.out.println(s2.compareTo(s3));//6
System.out.println(s1==s4);//7
System.out.println(s1.charAt(0));//8
System.out.println(s1.indexOf('j'));//9
System.out.println(s1.indexOf("to"));//10
System.out.println(s1.lastIndexOf('a'));//11
System.out.println(s1.lastIndexOf("o",15));//12
System.out.println(s1.length());//13
System.out.println(s1.substring(5));//14
System.out.println(s1.substring(5,11));//15
System.out.println(s1.startsWith("welc"));//16
System.out.println(s1.endsWith("java"));//17
System.out.println("welcome".trim());//18
System.out.println(s1.toLowerCase());//19
System.out.println(s1.toUpperCase());//20
System.out.println(s1.replace('o','T'));//21
System.out.println(s1.replaceFirst("o", "T"));//22
System.out.println(s1.replaceAll("o","T"));//23
System.out.println(s1.toCharArray());
}}
true    //1
false   //2 
true    //3
true    //4
0       //5
0       //6
true    //7  
w       //8
1       //9
8       //10
14      //11
9       //12
15      //13
me to java    //14
me to         //15
true          //16
true          //17
welcome       //18
welcome to java          //19
WELCOME TO JAVA          //20
welcTme tT java          //21
welcTme to java          //22
welcTme tT java          //23
welcome to java          //24