Java String类的常用方法（其它方法）

No.	方法名称	类型	描述
1	public String concat(String str)	普通	字符串连接，与"+"类似
2	public String toLowerCase()	普通	转小写
3	public String toUpperCase()	普通	转大写
4	public Sting trim()	普通	去掉字符串左右两边的空格，字符串中间空格保留
5	public int length()	普通	取得字符串长度
6	public String intern()	普通	数据入池
7	public boolean isEmpty()	普通	判断是否为空字符串(不是null,而是" ",长度0)

public class Demo {
public static void main(String[] args) {
String stra = "hello";
String strb = "hello " + "world";
String strc = "hello world";
System.out.println(stra == strb);//false
System.out.println(strb == strc);//true
}
}

public class Demo {
public static void main(String[] args) {
String stra = "hello";
String strb = stra + "world";// 等同于 String stb=stra.concat("world");
String strc = "hello world";
System.out.println(stra == strb);// false
System.out.println(strb == strc);// false
}
}

==========================================================public class Demo {
public static void main(String[] args) {
String str = "@@HelloWorld##";
System.out.println(str.toLowerCase());
System.out.println(str.toUpperCase());
}
}


==========================================================
public class Demo {
public static void main(String[] args) {
String str = " Hello World ";
System.out.println("【"+str+"】");
System.out.println("【"+str.trim()+"】");
}
}


==========================================================
public class Demo {
public static void main(String[] args) {
String str = "Hello World！";
System.out.println("字符串的长度为:" + str.length());
}
}


==========================================================
public class Demo {
public static void main(String[] args) {
String str = "Hello World！";
System.out.println("字符串是否为空:"+str.isEmpty());
}
}


==========================================================
public class Demo {
public static void main(String[] args) {
String str = "studentName";
System.out.println(initCap(str));
}

public static String initCap(String str) {
return str.substring(0, 1).toUpperCase() + str.substring(1);
}
}