Java中StringBuilder类的用法解析

public StringBuilder() {
        super(16); // 调用父类的构造方法，并默认初始化长度为16
}

AbstractStringBuilder(int capacity) {
    value = new char[capacity]; // 初始化一个长度为16的char型<strong>可变</strong>数组
}

public StringBuilder(String str) {
        super(str.length() + 16); // 通常调用父类的构造方法，但参数为传入字符串的长度＋16
        append(str); // 将入参str添加到stringbuilder中
    }

public StringBuilder(CharSequence seq) { // CharSequence 是一个描述字符串结构的接口，在这个接口里一共有三个常用的子类：String，StringBuffer，StringBuilder
        this(seq.length() + 16);
        append(seq);
    }

public StringBuilder append(StringBuffer sb) {
        super.append(sb);
        return this;
    }

@Override
public StringBuilder append(CharSequence s) {
        super.append(s);
        return this;
    }
   
@Override
public StringBuilder append(CharSequence s, int start, int end) {
        super.append(s, start, end);
        return this;
    }

@Override
public StringBuilder append(char[] str) {
        super.append(str);
        return this;
    }


@Override
public StringBuilder append(char[] str, int offset, int len) {
        super.append(str, offset, len);
        return this;
    }

@Override
public StringBuilder append(boolean b) { // 这里的入参还可以替换为char，int，float，long，double
        super.append(b);
        return this;
    }

@Override
public StringBuilder delete(int start, int end) {
        super.delete(start, end); // 删除[start, end)区间内的字符串
        return this;
    }

@Override
public StringBuilder deleteCharAt(int index) { // 删除指定索引位置的字符串
        super.deleteCharAt(index);
        return this;
    }

@Override
public StringBuilder insert(int index, char[] str, int offset, int len){
        super.insert(index, str, offset, len);
        return this;
    }

    
@Override
public StringBuilder insert(int offset, Object obj) {
        super.insert(offset, obj);
        return this;
    }

  
@Override
public StringBuilder insert(int offset, String str) {
        super.insert(offset, str);
        return this;
    }

@Override
public StringBuilder insert(int offset, char[] str) {
        super.insert(offset, str);
        return this;
    }


@Override
public StringBuilder insert(int dstOffset, CharSequence s) {
        super.insert(dstOffset, s);
        return this;
    }

@Override
public StringBuilder insert(int dstOffset, CharSequence s, int start, int end){
        super.insert(dstOffset, s, start, end);
        return this;
    }


@Override
public StringBuilder insert(int offset, boolean b) { // 这里的第二个入参还可以替换为char，int，float，long，double
        super.insert(offset, b);
        return this;
    }
    
@Override
public StringBuilder replace(int start, int end, String str) { // 替换方法
    super.replace(start, end, str);
    return this;
}

@Override
public int indexOf(String str) {
        return super.indexOf(str);
    }

@Override
public int indexOf(String str, int fromIndex) {
        return super.indexOf(str, fromIndex);
    }

@Override
public int lastIndexOf(String str) {
        return super.lastIndexOf(str);
    }

@Override
public int lastIndexOf(String str, int fromIndex) {
        return super.lastIndexOf(str, fromIndex);
    }

@Override
public StringBuilder reverse() {
        super.reverse();
        return this;
    }

@Override
public String toString() {
        // Create a copy, don't share the array
        return new String(value, 0, count); // 返回了一个新的String类型的字符串
    }