String类的常用方法

package stringUse;

public class StringUse {

    public static void main(String[] args) {

        //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);
    }

}