Java String 操作

我不是女神ヾ 2022-02-23 07:40 159阅读 0赞

### 是否包含字符串 ###

public boolean contains(CharSequence s) { 
        return indexOf(s.toString()) > -1;
    }
    
    public int indexOf(String str) { 
        return indexOf(str, 0);
    }
    
    public int lastIndexOf(String str) { 
        return lastIndexOf(str, value.length);
    }
    
    public boolean startsWith(String prefix) { 
        return startsWith(prefix, 0);
    }
    
    public boolean endsWith(String suffix) { 
        return startsWith(suffix, value.length - suffix.value.length);
    }

### 去除首位空白字符串 ###

public String trim() { 
        int len = value.length;
        int st = 0;
        char[] val = value;    /* avoid getfield opcode */
    
        while ((st < len) && (val[st] <= ' ')) { 
            st++;
        }
        while ((st < len) && (val[len - 1] <= ' ')) { 
            len--;
        }
        return ((st > 0) || (len < value.length)) ? substring(st, len) : this;
    }

### 提取字符串 ###

public String substring(int beginIndex) { 
        if (beginIndex < 0) { 
            throw new StringIndexOutOfBoundsException(beginIndex);
        }
        int subLen = value.length - beginIndex;
        if (subLen < 0) { 
            throw new StringIndexOutOfBoundsException(subLen);
        }
        return (beginIndex == 0) ? this : new String(value, beginIndex, subLen);
    }
    
    public String substring(int beginIndex, int endIndex) { 
        if (beginIndex < 0) { 
            throw new StringIndexOutOfBoundsException(beginIndex);
        }
        if (endIndex > value.length) { 
            throw new StringIndexOutOfBoundsException(endIndex);
        }
        int subLen = endIndex - beginIndex;
        if (subLen < 0) { 
            throw new StringIndexOutOfBoundsException(subLen);
        }
        return ((beginIndex == 0) && (endIndex == value.length)) ? this
                : new String(value, beginIndex, subLen);
    }

### 大小写转换 ###

public String toLowerCase() { 
        return toLowerCase(Locale.getDefault());
    }
    public String toUpperCase() { 
        return toUpperCase(Locale.getDefault());
    }

### 替换字符串 ###

public String replace(CharSequence target, CharSequence replacement) { 
        return Pattern.compile(target.toString(), Pattern.LITERAL).matcher(
        this).replaceAll(Matcher.quoteReplacement(replacement.toString()));
    }
    
    public String replaceAll(String regex, String replacement) { 
        return Pattern.compile(regex).matcher(this).replaceAll(replacement);
    }

### 分割与拼接 ###

public static String join(CharSequence delimiter, CharSequence... elements) { 
        Objects.requireNonNull(delimiter);
        Objects.requireNonNull(elements);
        // Number of elements not likely worth Arrays.stream overhead.
        StringJoiner joiner = new StringJoiner(delimiter);
        for (CharSequence cs: elements) { 
            joiner.add(cs);
        }
        return joiner.toString();
    }
    
    public String[] split(String regex) { 
        return split(regex, 0);
    }

### 字符串与byte转换 ###

byte[] data = "中文ABC".getBytes(StandardCharsets.UTF_8);
    String str  = new String(data,StandardCharsets.UTF_8);