技術標籤：java

StringBuffer常用方法

public static void bufferMethodDemo1(){
        StringBuffer sb = new StringBuffer();
        StringBuffer s1 = sb.append(4).append("s");
        s1.insert(1, " hello ");
        System.out.println(s1==sb);//true
        System.out.println(s1);//4 hello s
 

        System.out.println(sb);//4 hello s
        StringBuffer s2 = new StringBuffer("abc");
        s2.append(" xixi");
        s2.insert(2, " zz ");
        System.out.println(s2.toString());//ab zz c xixi
    }
    public static void bufferMethodDemo2(){
        StringBuffer s =
 
 new StringBuffer("hello");
        s.delete(1, 3);//hlo
        s.deleteCharAt(1);//ho
        s.replace(0, 1, "zx");//zxo
        s.setCharAt(2, 'q');//zxq
        //清空緩衝區
        // s = new StringBuffer();
        // s.delete(0, s.length());
        System.out.println(s);
    }

StringBuilder

public static void stringBuilderDemo(){
        //jdk1.5之後出現和StringBuffer一模一樣的物件，就是StringBuilder
        //優先使用StringBuilder，因為StringBuilder不同步，效率更高
        //StringBuilder不保證同步(通常用於單執行緒)，StringBuffer執行緒安全(通常用於多執行緒)
        //StringBuilder具有的方法與StringBuffer一樣
        StringBuilder sb = new StringBuilder();
        sb.append("hello");
        System.out.println(sb);
    }

將int型陣列變成字串

public static String arrayToString(int[] arr){
        String str = "[";
        for(int i=0;i<arr.length;i++){
            if(i!=arr.length-1)
            {
                str = str + arr[i]+",";
            }
            else
                str = str + arr[i]+"]";
        }
        return str;
    }
    public static StringBuilder arrayToString2(int[] arr){
        StringBuilder str = new StringBuilder("[");
        for(int i=0;i<arr.length;i++){
            if(i!=arr.length-1)
            {
                str = str.append(arr[i]+",");
            }
            else
                str = str.append(arr[i]+"]");
        }
        return str;
    }
}