String类的用法

package stringUse;


public class StringUse {


public static void main(String[] args) {
// TODO Auto-generated method stub
// String stra = new String("hello");
// String strb = new String("hello");
// System.out.println(stra == strb);    //false
// System.out.println(stra.equals((strb)));   //true
//
// String strc = "helloworld";
// String strd = "helloworld";
// System.out.println(strc == strd);//true
// System.out.println(strc.equals((strd)));//true




//获取
//indexOf,charAt(i),length(),substring,
String a1 = "hello";
sop(a1.indexOf("o",2));//4
sop(a1.indexOf("el"));//1
sop(a1.charAt(1));//e
sop(a1.length());//5
sop(a1.substring(1,4)); //ell

//判断
sop(a1.isEmpty());//false
sop(a1.contains("llo"));//true
sop(a1.startsWith("he"));//true
sop(a1.equals("hello"));//true
sop(a1.equalsIgnoreCase("hELLo"));  //true

//转换
String string1 = "  hello c++ ";
sop(string1.toUpperCase());//  HELLO C++ 
sop(string1); //  hello c++ 
sop(string1.trim());//hello c++

//replace
String str1 = "hello,java";
String str2 = str1.replace("java","C++");
sop("str1="+str1);//str1=hello,java
sop("str2="+str2);//str2=hello,C++

//split
String sentence = "aBBBcedBfstBBgk";
String[] arr = sentence.split("B");
sop("arr.length="+arr.length);//7
for(int i = 0; i<arr.length; i++){
sop(arr[i]);
}

//trans,字符串和字符数组转换
String strArr = "abcdfeg";
char[] array = strArr.toCharArray();
for(int i = 0; i<array.length; i++){
sop(array[i]);
}

char[] array2 = {'a','b','c','d','e','f'};
String arrStr = new String(array2, 1, 5);
sop(arrStr); //bcdef

//compareTo
String dang1 = "esun";  
String dang2 = "gsuz";  
sop(dang1.compareTo(dang2));//-2

//valueOf
int num = 12345;
String val = String.valueOf(num);
sop(val);
sop(val.length());//5,判断是几位数

}
public static void sop(Object obj){
System.out.println(obj);
}


}