常用类.可变字符串

package cyl4;

public class Demo04 {
    public static void main(String[] args) {
        //StringBuffer sb = new StringBuffer();
        StringBuilder sb = new StringBuilder();
        //1.append();追加
        sb.append("java");
        System.out.println(sb.toString());
        sb.append("JAVA");
        System.out.println(sb.toString());

        //2.insert();添加
        sb.insert(0,"最前面");
        System.out.println(sb.toString());

        //3.replace();替换
        sb.replace(0,3,"hello");//含头不含尾 end要+1
        System.out.println(sb.toString());

        //4.delete();删除
        sb.delete(0,5);
        System.out.println(sb.toString());

        //情况
        sb.delete(0,sb.length());
        System.out.println(sb.length());


    }
}

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