Summary of common methods for converting List＜String＞ to string form in Java (very complete!)

1. Basic conversion method (5 common methods)

1. Use  ()

This is a method introduced by Java 8, which is simple and fast, and is suitable for connecting list elements with fixed delimiters. For example, separate with commas. This is the simplest way, but the separator can only be a fixed string and cannot be changed dynamically.

List<String> list= ("A", "B", "C");
String result = (", ", list); // A, B, C

2. StringBuilder loop append

Manually traverse the list and use loop splicing strings. This allows for flexibility in handling each element, such as adding different separators between different elements, or adding specific characters at the beginning or end. But the code is relatively verbose and needs to deal with boundary conditions in the loop (such as the last element without delimiter).

// Good compatibility (full version of Java)List<String> list= ("A", "B", "C");
StringBuilder sb = new StringBuilder();
for (String s : list) {
    if (() > 0) {
        (" | ");
    }
    (s);
}
String result = (); // A | B | C

3. Java8 Stream API

Using Java 8's Stream and () can combine the processing power of the stream, such as filtering certain elements before splicing, or processing elements before splicing. For example, converting elements to uppercase and then joining is very useful for situations where elements need to be processed.

// Supports handling complex conversionsList<String> list= ("A", "B", "C");
String result = ()
        .map(String::toLowerCase) // Element processing example        .collect((" - ")); // a - b - c

4. Use third-party libraries: Apache Commons Lang or Guava library

List<String> list= ("A", "B", "C");

// Dependency needs to be introduced <commons-lang3>String result = (list, " \ "); // A \ B \ C


// Dependencies need to be introduced <Guava>String result = (", ").skipNulls().join(list); // Automatically jump null

Also note whether the list may be null or contains null elements. () will throw a NullPointerException when encountering a null element. Therefore, if there may be null in the list, it needs to be processed in advance, or use a third-party library method, such as () can automatically skip null. In this case, the user needs to be reminded to perform appropriate processing, or add a null value check in the code example.

2. Functional Advanced Scenario

1. With package format

// Add prefix suffixString jsonStyle = "[ " + (", ", list) + " ]";
// Output: [ A, B, C ]

2. Handle irregular structures

// Dynamically generate a list with sequence numbersStringBuilder sb = new StringBuilder();
for (int i = 0; i < (); i++) {
    ((i+1)+". "+(i)+"\n");
}
// Output: 1. A\n2. B\n3. C

3. Nested Conversion

// Multi-level list conversionList<List<String>> multiList = (
    ("A1", "A2"),
    ("B1", "B2")
);

String nestedResult = ()
    .map(subList -> "(" + ("/", subList) + ")")
    .collect((" → ")); 
// Output: (A1/A2) → (B1/B2)

3. Performance optimization suggestions (important!)

4. Special character processing skills

1. When retained characters

// Escape with HTML (example)String htmlSafe = ()
    .map(s -> StringEscapeUtils.escapeHtml4(s))  // commons-text
    .collect(("<br/>"));

2. CSV format conversion

// Handle comma scenariosString csv = ()
    .map(s -> "\"" + ("\"", "\"\"") + "\"") // Double quote escape    .collect((","));

Summarize

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